Pattern forming method, and resist composition, developer and rinsing solution used in the pattern forming method

ABSTRACT

A pattern forming method comprising a step of applying a resist composition whose solubility in a negative tone developer decreases upon irradiation with an actinic ray or radiation and which contains a resin having an alicyclic hydrocarbon structure and a dispersity of 1.7 or less and being capable of increasing the polarity by the action of an acid, an exposure step, and a development step using a negative tone developer; a resist composition for use in the method; and a developer and a rinsing solution for use in the method, are provided, whereby a pattern with reduced line edge roughness and high dimensional uniformity can be formed.

TECHNICAL FIELD

The present invention relates to a pattern forming method for use in theprocess of producing a semiconductor such as IC, in the production of acircuit board for liquid crystal, thermal head and the like, and in thelithography process of other photofabrications; a resist composition foruse in the pattern forming method; a developer for negative tonedevelopment used in the pattern forming method; and a rinsing solutionfor negative tone development used in the pattern forming method. Morespecifically, the present invention relates to a pattern forming methodsuitable for exposure with an ArF exposure apparatus using a lightsource that emits far ultraviolet light at a wavelength of 300 nm orless or with an immersion-type projection exposure apparatus; a resistcomposition for use in the pattern forming method; a developer fornegative tone development used in the pattern forming method; and arinsing solution for negative tone development used in the patternforming method.

BACKGROUND ART

Since the advent of a resist for KrF excimer laser (248 nm), an imageforming method called chemical amplification is used as an image formingmethod for a resist so as to compensate for sensitivity reduction causedby light absorption. For example, the image forming method by positivetone chemical amplification is an image forming method of decomposing anacid generator in the exposed area upon exposure to produce an acid,converting an alkali-insoluble group into an alkali-soluble group byusing the generated acid as a reaction catalyst in the baking afterexposure (PEB: Post Exposure Bake), and removing the exposed area byalkali development.

Along with miniaturization of a semiconductor device, there is becomingshorter the wavelength of the exposure light source and higher thenumerical aperture (higher NA) of the projection lens, and an exposuremachine using an ArF excimer laser having a wavelength of 193 nm as alight source has been so far developed. As commonly well known, thesefeatures can be expressed by the following formulae:

(Resolution)=k ₁·(λ/NA)

(Depth of focus)=±k ₂·λ/NA²

wherein λ is the wavelength of the exposure light source, NA is thenumerical aperture of the projection lens, and k₁ and k₂ arecoefficients related to the process.

A so-called immersion method of filling a high refractive-index liquid(hereinafter sometimes referred to as an “immersion liquid”) between theprojection lens and the sample has been conventionally advocated as atechnique for raising the resolution.

As for the “effect of immersion”, assuming that NA₀=sin θ, theabove-described resolution and depth of focus in the immersion can beexpressed by the following formulae:

(Resolution)=k ₁·(λ₁ /n)/NA₀

(Depth of focus)=±k ₂·(λ₀ /n)/NA₀ ²

wherein λ₀ is the wavelength of exposure light in air, n is therefractive index of the immersion liquid based on air, and θ is theconvergence half-angle of beam.

That is, the effect of immersion is equal to use of an exposurewavelength of 1/n. In other words, in the case of a projection opticalsystem with the same NA, the depth of focus can be made n times largerby the immersion. This is effective for all pattern profiles and can becombined with the super-resolution technology under study at present,such as phase-shift method and modified illumination method.

A double exposure technology or a double patterning technology is beingadvocated as a technique for more enhancing the resolution. This is tomake small k₁ in the above-described formula of resolution and ispositioned as a resolution-increasing technology.

In conventional pattern formation of an electronic device such assemiconductor device, a mask or reticle pattern in a size of 4 to 5times larger than the pattern intended to form is reduced andtransferred on an exposure target such as wafer by using a reductionprojection exposure apparatus.

However, the dimensional miniaturization brings about a problem that inthe conventional exposure system, lights irradiated on adjacent patternsinterfere with each other to decrease the optical contrast. Therefore,in such technology, it is devised to divide the exposure mask designinto two or more designs and synthesize an image by independentlyexposing these masks. In this double exposure system where the exposuremask design is divided, the image of the design must be againsynthesized on an exposure target (wafer) and therefore, the division ofthe mask design must be devised so that the pattern on the reticle canbe faithfully reproduced on the exposure target.

Studies of applying the effect of these double exposure systems to thetransfer of a fine image pattern of a semiconductor device areintroduced, for example, in Patent Document 1 (JP-A-2006-156422 (theterm “JP-A” as used herein means an “unexamined published Japanesepatent application”)).

Also, the recent progress of double exposure technology is reported, forexample, in Non-Patent Document 1 (SPIE Proc 5754, 1508 (2005)),Non-Patent Document 2 (SPIE Proc 5377, 1315 (2004)), and Non-PatentDocument 3 (SPIE Proc 61531K-1 (2006)).

However, in these double exposure systems, the pattern formation needsto be performed in the vicinity of resolution limit of the resist andthis incurs a problem that sufficient exposure margin or depth of focuscannot be obtained.

In other words, if a pattern forming process described, for example, inPatent Document 2 (JP-A-2001-109154) where a resist compositioncontaining a resin capable of increasing the polarity upon exposure iscoated on a substrate and the resist film is exposed and developed todissolve the exposed area with an alkali developer, or a pattern formingprocess described, for example, in Patent Document 3 (JP-A-2003-76019)where a resist composition containing a resin capable of increasing themolecular weight upon exposure is coated on a substrate and the resistfilm is exposed and developed to dissolve the unexposed area with analkali developer, is applied to a double exposure process, asufficiently high resolving performance cannot be obtained.

With respect to the developer for g-line, i-line, KrF, ArF, EB or EUVlithography, an aqueous alkali developer of 2.38 mass % TMAH(tetramethylammonium hydroxide) is being used at present as ageneral-purpose developer.

Other than the above-described developer, for example, Patent Document 4(JP-A-2001-215731) describes a developer for developing a resistmaterial containing a copolymer of a styrene-based monomer and anacryl-based monomer and dissolving the exposed portion, where thedeveloper contains an aliphatic linear ether-based solvent or aromaticether-based solvent and a ketone-based solvent having a carbon number of5 or more; Patent Document 5 (JP-A-2006-227174) describes a developerfor developing a resist material capable of decreasing the molecularweight as a result of breakage of the polymer chain upon irradiationwith radiation, thereby dissolving the exposed portion, where thedeveloper has at least two or more acetic acid groups, ketone groups,ether groups or phenyl groups and has a molecular weight of 150 or more;and Patent Document 6 (JP-A-6-194847) describes a developer fordeveloping a resist material mainly composed of a photosensitivepolyhydroxy ether resin obtained by the reaction of a polyhydroxy etherresin with a diglycidyl (meth)acrylate, where the developer is anaromatic compound having a carbon number of 6 to 12 or a mixed solventcontaining 50 mass % or more of an aromatic compound having a carbonnumber of 6 to 12.

However, these combinations of the resist composition and the developermentioned above merely provide a system of forming a pattern bycombining a specific resist composition with a high-polarity alkalideveloper or a developer containing a low-polarity organic solvent.

That is, as shown in FIG. 1, in the case of a positive tone system (acombination of a resist composition and a positive tone developer), amaterial system of performing the pattern formation by selectivelydissolving and removing a region having strong light irradiationintensity out of an optical aerial image (light intensity distribution)is merely provided. On the other hand, as for the combination of anegative tone system (a resist composition and a negative tonedeveloper), a material system of performing the pattern formation byselectively dissolving and removing a region having a weak lightirradiation intensity is merely provided.

The term “positive tone developer” as used herein indicates a developerthat selectively dissolves and removes the exposed area not lower than apredetermined threshold value shown by a solid line in FIG. 1, and the“negative tone developer” indicates a developer that selectivelydissolves and removes the exposed area not higher than the predeterminedthreshold value. A development step using a positive tone developer iscalled a positive tone development (sometimes referred to as a positivetone development step), and a development step using a negative tonedeveloper is called a negative tone development (sometimes referred toas a negative tone development step).

Patent Document 7 (JP-A-2000-199953) describes a double developmenttechnology as the double patterning technology for improving theresolution. In this case, an image forming method by chemicalamplification in general is utilized, and by making use of a propertythat the polarity of a resin in a resist composition when exposedbecomes a high polarity in a region irradiated with a high lightintensity and becomes a low polarity in a region irradiated with a lowlight intensity, positive tone development is performed by dissolving ahigh exposure region of the resist film with a high-polarity developer,while negative tone development is performed by dissolving a lowexposure region with a low-polarity developer. More specifically, theregion not lower than an exposure dose of E2 in FIG. 2 is dissolvedusing an aqueous alkali solution as the positive tone developer, theregion not higher than an exposure dose of E1 is dissolved using aspecific organic solvent as the negative tone developer, and, as shownin FIG. 2, the region with a medium exposure dose (E2 to E1) is allowedto remain without being developed, whereby an L/S pattern 3 with a pitchhalf the pitch of the exposure mask 2 pattern is formed on a wafer 4.

Patent Document 1: JP-A-2006-156422

Patent Document 2: JP-A-2001-109154

Patent Document 3: JP-A-2003-76019

Patent Document 4: JP-A-2001-215731

Patent Document 5: JP-A-2006-227174

Patent Document 6: JP-A-6-194847

Patent Document 7: JP-A-2000-199953

Non-Patent Document 1: SPIE Proc 5754, 1508 (2005)

Non-Patent Document 2: SPIE Proc 5377, 1315 (2004)

Non-Patent Document 3: SPIE Proc 61531k-1 (2006)

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

In the conventional double development technology, a tert-butyl group isemployed as an acid-decomposable group in the resin contained in theresist composition and therefore, the resin is insufficient to bring outa polarity change large enough to cause a difference in the dissolutioncharacteristics by a chemical amplification reaction associated with theexposure.

Furthermore, since a resin having a styrene skeleton is used as theresin in the resist composition, the polarity in the low exposure regionof the resist film becomes high and this causes a problem that thedevelopment rate at the development using a negative tone developer islow and the developability when using a negative tone developer is bad.

An object of the present invention is to solve these problems andprovide a pattern forming method for stably forming a high-precisionfine pattern particularly by reducing the line edge roughness andraising the dimensional uniformity of the pattern so as to produce ahighly integrated electronic device with high precision.

Means for Solving the Problems

The present invention has the following constructions, and the object ofthe present invention can be attained by these constructions.

(1) A pattern forming method, comprising:

(i) a step of applying a resist composition whose solubility in apositive tone developer increases and solubility in a negative tonedeveloper decreases upon irradiation with an actinic ray or radiationand which contains a resin having an alicyclic hydrocarbon structure anda dispersity of 1.7 or less and being capable of increasing a polarityof the resin by an action of an acid;

(ii) an exposure step; and

(iv) a development step using a negative tone developer.

(2) A pattern forming method, comprising:

(i) a step of applying a resist composition whose solubility in apositive tone developer increases and solubility in a negative tonedeveloper decreases upon irradiation with an actinic ray or radiationand which contains a resin having an alicyclic hydrocarbon structure anda weight average molecular weight of 6,000 or less and being capable ofincreasing a polarity of the resin by an action of an acid;

(ii) an exposure step; and

(iv) a development step using a negative tone developer.

(3) A pattern forming method, comprising:

(i) a step of applying a resist composition whose solubility in apositive tone developer increases and solubility in a negative tonedeveloper decreases upon irradiation with an actinic ray or radiationand which contains a resin having an alicyclic hydrocarbon structure, adispersity of 1.7 or less and a weight average molecular weight of 6,000or less and being capable of increasing a polarity of the resin by anaction of an acid;

(ii) an exposure step; and

(iv) a development step using a negative tone developer.

(4) The pattern forming method according to any one of (1) to (3) above,wherein (iv) the development step using a negative tone developer is astep performed using a developer containing at least one kind of asolvent selected from organic solvents and having a vapor pressure of 5kPa or less at 20° C.

(5) The pattern forming method as described in any one of (1) to (4)above, which further comprises:

(vi) a washing step using a rinsing solution containing an organicsolvent.

(6) The pattern forming method as described in (5) above, wherein therinsing solution containing an organic solvent is a rinsing solutionhaving a vapor pressure of 0.1 kPa or more at 20° C.

(7) The pattern forming method as described in any one of (1) to (6),which further comprises:

(iii) a development step using a positive tone developer.

(8) A resist composition for negative tone development, comprising:

(a1) a resin having an alicyclic hydrocarbon structure and a dispersityof 1.7 or less and being capable of increasing a polarity of the resinby an action of an acid;

(B) a photo-acid generator; and

(C) a solvent.

(9) A resist composition for negative tone development, comprising:

(a2) a resin having an alicyclic hydrocarbon structure and a weightaverage molecular weight of 6,000 or less and being capable ofincreasing a polarity of the resin by an action of an acid;

(B) a photo-acid generator; and

(C) a solvent.

(10) A resist composition for negative tone development, comprising:

(a3) a resin having an alicyclic hydrocarbon structure, a dispersity of1.7 or less and a weight average molecular weight of 6,000 or less andbeing capable of increasing a polarity of the resin by an action of anacid;

(B) a photo-acid generator; and

(C) a solvent.

(11) A resist composition for multiple development, comprising:

(a1) a resin having an alicyclic hydrocarbon structure and a dispersityof 1.7 or less and being capable of increasing a polarity of the resinby an action of an acid;

(B) a photo-acid generator; and

(C) a solvent.

(12) A resist composition for multiple development, comprising:

(a2) a resin having an alicyclic hydrocarbon structure and a weightaverage molecular weight of 6,000 or less and being capable ofincreasing a polarity of the resin by an action of an acid;

(B) a photo-acid generator; and

(C) a solvent.

(13) A resist composition for multiple development, comprising:

(a3) a resin having an alicyclic hydrocarbon structure, a dispersity of1.7 or less and a weight average molecular weight of 6,000 or less andbeing capable of increasing a polarity of the resin by an action of anacid;

(B) a photo-acid generator; and

(C) a solvent.

(14) A developer for negative tone development, which is used in thepattern forming method described in any one of (1) to (7) above, thedeveloper comprising an organic solvent and having a vapor pressure of 5kPa or less at 20° C.

(15) A rinsing solution for negative tone development, which is used inthe pattern forming method described in any one of (1) to (7) above, therinsing solution comprising an organic solvent and having a vaporpressure of 0.1 kPa or more at 20° C.

(16) The pattern forming method as described in any one of (1) to (7)above, wherein (ii) the exposure step is performed by using an ArFexcimer laser.

(17) The pattern forming method as described in any one of (1) to (7)and (16) above,

wherein the negative tone developer is at least one selected from thegroup consisting of ketone-based solvent, ester-based solvent,alcohol-based solvent, amide-based solvent, ether-based solvent andhydrocarbon-based solvent.

ADVANTAGE OF THE INVENTION

According to the present invention, a method of stably forming ahigh-precision fine pattern with reduced line edge roughness and highdimensional uniformity, a resist composition for negative tonedevelopment or multiple development used in the method, a developer fornegative tone development used in the method, and a rinsing solution fornegative tone development used in the method can be provided.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view showing the relationship among positive tonedevelopment, negative tone development and exposure dose.

FIG. 2 is a schematic view showing the pattern forming method usingpositive tone development and negative tone development in combination.

FIG. 3 is a schematic view showing the relationship among positive tonedevelopment, negative tone development and exposure dose.

FIG. 4 is a graph showing the relationship between exposure dose andresidual film curve when a positive tone developer or a negative tonedeveloper is used.

FIG. 5 is a schematic view showing the relationship among positive tonedevelopment, negative tone development and exposure dose.

FIG. 6 is a schematic view showing the relationship among positive tonedevelopment, negative tone development and exposure dose in the methodof the present invention.

FIG. 7 is a schematic view showing the relationship among positive tonedevelopment, negative tone development and exposure dose.

FIG. 8 is a view showing the spatial intensity distribution of anoptical image.

FIG. 9 is a schematic view showing the relationship among positive tonedevelopment, threshold value (a) and light intensity.

FIG. 10 is a schematic view showing the spatial intensity distributionof an optical image.

FIG. 11 is a schematic view showing the relationship among negative tonedevelopment, threshold value (b) and light intensity.

BEST MODE FOR CARRYING OUT THE INVENTION

The best mode for carrying out the present invention is described below.

Incidentally, in the present invention, when a group (atomic group) isdenoted without specifying whether substituted or unsubstituted, thegroup includes both a group having no substituent and a group having asubstituent. For example, an “alkyl group” includes not only an alkylgroup having no substituent (unsubstituted alkyl group) but also analkyl group having a substituent (substituted alkyl group).

First, the terms used in the context of the present invention aredescribed. The pattern forming system includes a positive tone systemand a negative tone system and in either system, a change in thesolubility of a resist film in a developer due to a chemical reactiontriggered by light irradiation is utilized. A system where thelight-irradiated part dissolves in a developer is called a positive tonesystem, and a system where the light-unirradiated part dissolves in adeveloper is called a negative tone system. The developer used hereincludes two types of developers, that is, a positive tone developer anda negative tone developer. The positive tone developer is a developerthat selectively dissolves and removes the exposed area not lower than apredetermined threshold value shown in FIG. 1, and the negative tonedeveloper is a developer that selectively dissolves and removes anexposed area not higher than the above-described threshold value. Adevelopment step using a positive tone developer is called a positivetone development (sometimes referred to as a positive tone developmentstep), and a development step using a negative tone developer is calleda negative tone development (sometimes referred to as a negative tonedevelopment step).

The present invention provides, as a technique for raising theresolution, a new pattern forming method by a combination of a developer(negative tone developer) for selectively dissolving and removing theexposed area not higher than a predetermined threshold value (b) asshown in FIG. 3, with a resist composition for negative tonedevelopment, which contains a resin that increases the polarity by theaction of an acid and forms a film whose solubility in a positive tonedeveloper (preferably an alkali developer) increases and solubility in anegative tone developer (preferably an organic developer) decreases uponirradiation with an actinic ray or radiation.

The present invention provides, as a technique for raising theresolution, a new pattern forming method preferably by a combination ofa developer (positive tone developer) for selectively dissolving andremoving the exposed area not lower than a predetermined threshold value(a) and a developer (negative tone developer) for selectively dissolvingand removing the exposed area not higher than a predetermined thresholdvalue (b), with a resist composition for multiple development, whichforms a film whose solubility in a positive tone developer (preferablyan alkali developer) increases and solubility in a negative tonedeveloper (preferably an organic developer) decreases upon irradiationwith an actinic ray or radiation.

That is, as shown in FIG. 3, when a pattern element on an exposure maskis projected on a wafer by light irradiation, the region having a stronglight irradiation intensity (the exposed area not lower than apredetermined threshold value (a)) is dissolved and removed using apositive tone developer and the region having a weak light irradiationintensity (the exposed area not higher than a predetermined thresholdvalue (b)) is dissolved and removed using a negative tone developer,whereby a pattern with resolution as high as 2 times the frequency ofthe optical spatial image (light intensity distribution) can beobtained. Also, in the method of the present invention, the design ofthe exposure mask need not be divided.

As regards the resist composition for multiple development whenperforming those two or more development operations at the same time, aresist composition for negative tone development may be used as it is.

The pattern forming process necessary for practicing the presentinvention comprises the following steps:

(i) a step of coating a substrate with a resist composition whosesolubility in a negative tone developer decreases upon irradiation withan actinic ray or radiation,

(ii) an exposure step, and

(iv) a step of developing the resist film with a negative tonedeveloper.

The pattern forming method of the present invention preferably furthercomprises (vi) a step of washing the resist film with a rinsing solutionfor negative tone development.

The pattern forming method of the present invention preferably furthercomprises (iii) a step of developing the resist film with a positivetone developer.

The pattern forming method of the present invention preferably comprises(v) a heating step after the exposure step (ii).

In the pattern forming method of the present invention, the exposurestep (ii) may be performed a plurality of times.

In the pattern forming method of the present invention, the heating step(v) may be performed a plurality of times.

In practicing the present invention, (a) a resist composition whosesolubility in a negative tone developer decreases upon irradiation withan actinic ray or radiation and which contains a resin having analicyclic hydrocarbon structure and a dispersity (molecular weightdistribution, Mw/Mn) of 1.7 or less and/or a weight average molecularweight of 6,000 or less and being capable of increasing the polarity bythe action of an acid, and (b) a negative tone developer (preferably anorganic developer) are necessary.

In practicing the present invention, (c) a rinsing solution for negativetone development is preferably further used.

In practicing the present invention, (d) a positive tone developer(preferably an alkali developer) is preferably further used.

In the present invention, a pattern forming process using two kinds ofdevelopers, that is, a positive tone developer and a negative tonedeveloper, is preferred. In this case, the order of developments is notparticularly limited, but it is preferred to perform development byusing a positive tone developer or a negative tone developer after firstexposure and then perform negative or positive tone development by usinga developer different from that in the first development. After thenegative tone development, the resist film is preferably washed with anorganic solvent-containing rinsing solution for negative tonedevelopment.

The pattern forming system includes a positive tone system and anegative tone system and in either system, a change in the solubility ofa resist film in a developer due to a chemical reaction triggered bylight irradiation is utilized. In general, a system where thelight-irradiated part dissolves in a developer is called a positive tonesystem, and a system where the light-unirradiated part dissolves in adeveloper is called a negative tone system. The positive tone resistutilizes a chemical reaction such as polarity conversion for enhancingthe solubility in a developer, and the negative tone resist utilizesbond formation between molecules, such as crosslinking reaction orpolymerization reaction.

Since the advent of a resist for KrF excimer laser (248 nm), an imageforming method called chemical amplification is used as an image formingmethod for a resist so as to compensate for sensitivity reduction causedby light absorption. For example, the image forming method by positivetone chemical amplification is an image forming method of decomposing anacid generator in the exposed area upon exposure to generate an acid,converting an alkali-insoluble group into an alkali-soluble group byusing the generated acid as a reaction catalyst in the baking afterexposure (PEB: Post Exposure Bake), and removing the exposed area byalkali development.

In the present invention, one positive tone resist composition (a) actsas a positive tone resist for a positive tone developer and at the sametime, acts as a negative tone resist for a negative tone developer.

In the present invention, an alkali developer (aqueous) can be used asthe positive tone developer, and an organic developer containing anorganic solvent can be used as the negative tone developer.

Also, the resist composition (a) is a “resin composition that forms afilm capable of increasing the polarity as a result of a chemicalreaction triggered by exposure to irradiation”.

In conventionally employed negative tone image-forming systems, amaterial system utilizing a mechanism of increasing the molecular weightexclusively by the bonding between molecules and decreasing thesolubility in a developer has been proposed. However, it has beendifficult for the image forming mechanism utilizing a change in themolecular weight to establish a system of allowing one resist materialsystem to act as a positive tone resist for one developer and act as anegative tone resist for another developer.

In the present invention, the resist composition (a) not only causes adecrease of the solubility in a negative tone developer due to apolarity conversion reaction of the polymer side chain but also bringsabout both an increase of the solubility in an alkali developer and adecrease of the solubility in an organic developer particularly byvirtue of a specific chemical reaction (the polarity conversion reactionof the polymer side chain) at the same time.

In the present invention, the matter of importance is to control the“threshold value” of exposure dose (the exposure dose for solubilizingor insolubilizing the film by a developer in the light-irradiatedregion). The “threshold value” is the minimum exposure dose forsolubilizing the film by a positive tone developer and the maximumexposure dose for insolubilizing the film by a negative tone developerso as to obtain a desired line width at the time of performing patternformation.

The “threshold value” can be determined as follows.

That is, the “threshold value” is the maximum exposure dose forsolubilizing the film by a positive tone developer and the minimumexposure dose for insolubilizing the film by a negative tone developerso as to obtain a desired line width at the time of performing patternformation.

More strictly, the threshold value is defined as follows.

The residual film ratio of the resist film to the exposure dose ismeasured and at this time, as shown in FIG. 4, the minimum exposure dosegiving a residual film ratio of 0% for the positive tone developer isdesignated as a threshold value (a) and the minimum exposure dose givinga residual film ratio of 100% for the negative tone developer isdesignated as a threshold value (b).

For example, as shown in FIG. 5, the threshold value (a) of the exposuredose for solubilizing the film by a positive tone developer is set to behigher than the threshold value (b) for solubilizing the film by anegative tone developer, whereby pattern formation can be achieved byone exposure operation. That is, as shown in FIG. 6, after a resist iscoated on a wafer and exposed, the portion not lower than the thresholdvalue (a) of the exposure dose is dissolved with a positive tonedeveloper and then, the region not higher than the threshold value (b)of the exposure dose is dissolved with a negative tone developer,whereby pattern formation can be performed by one exposure operation. Inthis case, as for the order of the development with a positive tonedeveloper and the development with a negative tone developer, eitherdevelopment may be performed earlier. After the negative tonedevelopment, when the resist film is washed with a rinsing solutioncontaining an organic solvent, more successful pattern formation can beachieved.

The method for controlling the threshold value includes a method ofcontrolling the material-related parameters of the resist composition(a) and the developer or controlling the parameters related to theprocess.

As for the material-related parameter, control of various physicalvalues related to solubility of the resist composition (a) in thedeveloper and the organic solvent, such as SP value (solubilityparameter) and LogP value, is effective. Specific examples of theparameter include, for the polymer contained in the resist composition(a), the average molecular weight, the molecular weight dispersity, themonomer compositional ratio, the polarity of monomer, the monomersequence, the polymer blend and the addition of low molecular additive,and for the developer, include the concentration of developer, theaddition of low molecular additive and the addition of surfactant.

Also, specific examples of the process-related parameter include thefilm formation temperature, the film formation time, the temperature andtime of post-heating after exposure, the temperature at development, thedevelopment time, the nozzle system (puddle method) of developingapparatus, and the rinsing method after development.

Accordingly, for obtaining a good pattern in the pattern forming methodusing negative tone development as well as in the pattern forming methodby multiple development using negative tone development and positivetone development in combination, it is important to combine theabove-described material-related parameters and process parameters whileappropriately controlling these parameters.

The pattern forming process using two kinds of developers, namely, apositive tone developer and a negative tone developer, may be a processwhere the exposure is performed once as described above or where theexposure is performed two or more times by the following process. Thatis, development using a positive tone developer or a negative tonedeveloper is performed after first exposure, and negative or positivetone development using a developer different from that in the firstdevelopment is performed after second exposure.

A pattern forming method comprising, in order:

(i) a step of coating a substrate with a resist composition for multipledevelopment, whose solubility in a positive tone developer increases andsolubility in a negative tone developer decreases upon irradiation withan actinic ray or radiation,

(ii-1) a first exposure step,

(v-1) a first heating step,

(iii) a step of developing the resist film with a positive tonedeveloper,

(ii-2) a second exposure step,

(v-2) a second heating step, and

(iv) a step of developing the resist film with a negative tonedeveloper.

A pattern forming method comprising, in order:

(i) a step of coating a substrate with a resist composition for multipledevelopment, whose solubility in a positive tone developer increases andsolubility in a negative tone developer decreases upon irradiation withan actinic ray or radiation,

(ii-1) a first exposure step,

(v-1) a first heating step,

(iv) a step of developing the resist film with a negative tonedeveloper,

(ii-2) a second exposure step,

(v-2) a second heating step, and

(iii) a step of developing the resist film with a positive tonedeveloper.

As regards the resist composition for multiple development, the resistcomposition described later can be used.

When exposure is performed two or more times, this is advantageous inthat the latitude of control of the threshold value in the developmentafter first exposure and control of the threshold value in thedevelopment after second exposure increases.

In the case of performing the exposure two or more times, the secondexposure dose is preferably set to be larger than the first exposuredose. Because, as shown in FIG. 7, in the second development, thethreshold value is determined based on the amount to which the historyof first and second exposure doses are added, and when the secondexposure dose is sufficiently larger than the first exposure dose, theeffect of the first exposure dose is reduced and depending on the case,can be neglected.

The exposure dose (Eo1 [mJ/cm²]) in the step of performing the firstexposure is preferably 5 [mJ/cm²] or more smaller than the exposure dose(Eo2 [mJ/cm²]) in the step of performing the second exposure. In thiscase, the history of the first exposure can be made to less affect theprocess of performing pattern formation by the second exposure.

In the case of performing the exposure two times, the first developmentis not limited to positive tone development, and development using anegative tone developer may be performed first.

For changing the first exposure dose and the second exposure dose, amethod of adjusting the above-described various parameters related tothe material and process is effective. In particular, control of thetemperature in the first heating step and the temperature in the secondheating step is effective. That is, in order to make the first exposuredose to be smaller than the second exposure dose, it is effective to setthe temperature in the first heating step to be lower than thetemperature in the second heating step.

The threshold value (a) in the positive tone development is determinedas follows in the actual lithography process.

A film composed of a resist composition whose solubility in a positivetone developer increases and solubility in a negative tone developerdecreases upon irradiation with an actinic ray or radiation is formed ona substrate, and the resist film is exposed through a photomask having adesired pattern size under desired illumination conditions. At thistime, the exposure is performed by varying the exposure focus in 0.05[μm] steps and the exposure dose in 0.5 [mJ/cm²] steps.

After the exposure, the resist film is heated at a desired temperaturefor a desired time and then developed with an alkali developer in adesired concentration for a desired time. After the development, theline width of the pattern is measured using CD-SEM, and the exposuredose A [mJ/cm²] and focus position for forming a desired line width aredetermined. Subsequently, the intensity distribution of an optical imagewhen the above-described photomask is irradiated with a specificexposure dose A [mJ/cm²] and a specific focus position is calculated.The calculation can be performed using a simulation software (Prolith,ver. 9.2.0.15, produced by KLA). Details of the calculation method aredescribed in Chris. A. Mack, Inside PROLITH, Chapter 2, “Aerial ImageFormation”, FINLE Technologies, Inc.

As a result of calculation, for example, the spatial intensitydistribution shown in FIG. 8 of an optical image is obtained.

Here, as shown in FIG. 9, the light intensity at a position after thespatial position is shifted by ½ of the obtained pattern line width fromthe minimum value in the spatial intensity distribution of an opticalimage becomes the threshold value (a).

The threshold value (b) in the negative tone development is determinedas follows in the actual lithography process.

A film composed of a resist composition whose solubility in a positivetone developer increases and solubility in a negative tone developerdecreases upon irradiation with an actinic ray or radiation is formed ona substrate, and the resist film is exposed through a photomask having adesired pattern size under desired illumination conditions. At thistime, the exposure is performed by varying the exposure focus in 0.05[μm] steps and the exposure dose in 0.5 [mJ/cm²] steps.

After the exposure, the resist film is heated at a desired temperaturefor a desired time and then developed with an organic developer in adesired concentration for a desired time. After the development, theline width of the pattern is measured using CD-SEM, and the exposuredose A [mJ/cm²] and focus position for forming a desired line width aredetermined. Subsequently, the intensity distribution of an optical imagewhen the above-described photomask is irradiated with a specificexposure dose A [mJ/cm²] and a specific focus position is calculated.The calculation is performed using a simulation software (Prolith,produced by KLA).

For example, a spatial intensity distribution shown in FIG. 10 of anoptical image is obtained.

Here, as shown in FIG. 11, the light intensity at a position after thespatial position is shifted by ½ of the obtained pattern line width fromthe maximum value in the spatial intensity distribution of an opticalimage is defined as the threshold value (b).

The threshold value (a) is preferably from 0.1 to 100 [mJ/cm²], morepreferably from 0.5 to 50 [mJ/cm²], still more preferably from 1 to 30[mJ/cm²]. The threshold value (b) is preferably from 0.1 to 100[mJ/cm²], more preferably from 0.5 to 50 [mJ/cm²], still more preferablyfrom 1 to 30 [mJ/cm²].

The difference between threshold values (a) and (b) is preferably from0.1 to 80 [mJ/cm²], more preferably from 0.5 to 50 [mJ/cm²], still morepreferably from 1 to 30 [mJ/cm²].

At the time of performing positive tone development, an alkali developeris preferably used.

The alkali developer which can be used in performing positive tonedevelopment is, for example, an alkaline aqueous solution of inorganicalkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate,sodium silicate, sodium metasilicate and aqueous ammonia, primary aminessuch as ethylamine and n-propylamine, secondary amines such asdiethylamine and di-n-butylamine, tertiary amines such as triethylamineand methyldiethyl-amine, alcohol amines such as dimethylethanolamine andtriethanolamine, quaternary ammonium salts such as tetramethylammoniumhydroxide and tetraethylammonium hydroxide, and cyclic amines such aspyrrole and piperidine.

Furthermore, this alkaline aqueous solution may be used after addingthereto alcohols and a surfactant each in an appropriate amount.

The alkali concentration of the alkali developer is usually from 0.1 to20 mass %.

The pH of the alkali developer is usually from 10.0 to 15.0.

In particular, an aqueous 2.38% tetramethylammonium hydroxide solutionis preferred.

As for the rinsing solution in the rinsing treatment performed afterpositive tone development, pure water is used, and the pure water may beused after adding thereto a surfactant in an appropriate amount.

At the time of performing negative tone development, an organicdeveloper containing an organic solvent is preferably used.

As for the organic developer which can be used in performing negativetone development, a polar solvent such as ketone-based solvent,ester-based solvent, alcohol-based solvent, amide-based solvent andether-based solvent, and a hydrocarbon-based solvent can be used. Forexample, there may be used a ketone-based solvent such as 1-octanone,2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone, 2-hexanone,diisobutyl ketone, cyclohexanone, methylcyclohexanone, phenylacetone,methyl ethyl ketone and methyl isobutyl ketone; and an ester-basedsolvent such as methyl acetate, butyl acetate, ethyl acetate, isopropylacetate, amyl acetate, propylene glycol monomethyl ether acetate,ethylene glycol monoethyl ether acetate, diethylene glycol monobutylether acetate, diethylene glycol monoethyl ether acetate,ethyl-3-ethoxypropionate, 3-methoxybutyl acetate,3-methyl-3-methoxybutyl acetate, methyl formate, ethyl formate, butylformate, propyl formate, ethyl lactate, butyl lactate and propyllactate.

Examples of the alcohol-based solvent include an alcohol such as methylalcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butylalcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol,n-hexyl alcohol, n-heptyl alcohol, n-octyl alcohol and n-decanol; aglycol-based solvent such as ethylene glycol, diethylene glycol andtriethylene glycol; and a glycol ether-based solvent such as ethyleneglycol monomethyl ether, propylene glycol monomethyl ether, ethyleneglycol monoethyl ether, propylene glycol monoethyl ether, diethyleneglycol monomethyl ether, triethylene glycol monoethyl ether andmethoxymethyl butanol.

Examples of the ether-based solvent include, in addition to the glycolether-based solvents above, dioxane and tetrahydrofuran.

Examples of the amide-based solvent which can be used includeN-methyl-2-pyrrolidone, N,N-dimethylacetamide and N,N-dimethylformamide.

Examples of the hydrocarbon-based solvent include an aromatichydrocarbon-based solvent such as toluene and xylene, and an aliphatichydrocarbon-based solvent such as pentane, hexane, octane and decane.

A plurality of these solvents may be mixed, or the solvent may be usedby mixing it with a solvent other than those described above or water.

As regards the development system, for example, a method of raising thedeveloper on a substrate surface by the effect of a surface tension andkeeping it still for a fixed time, thereby performing the development(puddle method), a method of spraying the developer on a substratesurface (spray method), and a method of continuously ejecting thedeveloper on a substrate rotating at a constant speed while scanning thedeveloper ejecting nozzle at a constant rate (dynamic dispense method)may be applied. In using such a development method, if the vaporpressure of the negative tone developer is high, the substrate surfaceis cooled due to evaporation of the developer to reduce the temperatureof the developer and the film of the resist composition formed on thesubstrate is not dissolved at a constant rate, giving rise todeterioration of the dimensional uniformity. For this reason, the vaporpressure at 20° C. of the developer which can be used in performingnegative tone development is preferably 5 kPa or less, more preferably 3kPa or less, and most preferably 2 kPa or less.

Specific examples of the developer having a vapor pressure of 5 kPa orless at 20° C. include a ketone-based solvent such as 1-octanone,2-octanone, 1-nonanone, 2-nonanone, 4-heptanone, 2-hexanone, diisobutylketone, cyclohexanone, methylcyclohexanone, phenylacetone and methylisobutyl ketone; an ester-based solvent such as butyl acetate, amylacetate, propylene glycol monomethyl ether acetate, ethylene glycolmonoethyl ether acetate, diethylene glycol monobutyl ether acetate,diethylene glycol monoethyl ether acetate, ethyl-3-ethoxypropionate,3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, butyl formate,propyl formate, ethyl lactate, butyl lactate and propyl lactate; analcohol-based solvent such as n-propyl alcohol, isopropyl alcohol,n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutylalcohol, n-hexyl alcohol, n-heptyl alcohol, n-octyl alcohol andn-decanol; a glycol-based solvent such as ethylene glycol, diethyleneglycol and triethylene glycol; a glycol ether-based solvent such aspropylene glycol monomethyl ether, ethylene glycol monoethyl ether,propylene glycol monoethyl ether, diethylene glycol monomethyl ether,triethylene glycol monoethyl ether and methoxymethylbutanol; anether-based solvent such as tetrahydrofuran; an amide-based solvent suchas N-methyl-2-pyrrolidone, N,N-dimethylacetamide andN,N-dimethylformamide; an aromatic hydrocarbon-based solvent such astoluene and xylene; and an aliphatic hydrocarbon-based solvent such asoctane and decane.

Specific examples of the developer having a vapor pressure of 2 kPa orless at 20° C., which is a most preferred range, include a ketone-basedsolvent such as 1-octanone, 2-octanone, 1-nonanone, 2-nonanone,4-heptanone, 2-hexanone, diisobutyl ketone, cyclohexanone,methylcyclohexanone and phenylacetone; an ester-based solvent such asbutyl acetate, amyl acetate, propylene glycol monomethyl ether acetate,ethylene glycol monoethyl ether acetate, diethylene glycol monobutylether acetate, diethylene glycol monoethyl ether acetate,ethyl-3-ethoxypropionate, 3-methoxybutyl acetate,3-methyl-3-methoxybutyl acetate, ethyl lactate, butyl lactate and propyllactate; an alcohol-based solvent such as n-butyl alcohol, sec-butylalcohol, tert-butyl alcohol, isobutyl alcohol, n-hexyl alcohol, n-heptylalcohol, n-octyl alcohol and n-decanol; a glycol-based solvent such asethylene glycol, diethylene glycol and triethylene glycol; a glycolether-based solvent such as propylene glycol monomethyl ether, ethyleneglycol monoethyl ether, propylene glycol monoethyl ether, diethyleneglycol monomethyl ether, triethylene glycol monoethyl ether andmethoxymethylbutanol; an amide-based solvent such asN-methyl-2-pyrrolidone, N,N-dimethylacetamide and N,N-dimethylformamide;an aromatic hydrocarbon-based solvent such as xylene; and an aliphatichydrocarbon-based solvent such as octane and decane.

In the developer usable when performing negative tone development, asurfactant can be added in an appropriate amount, if desired.

The surfactant is not particularly limited but, for example, an ionic ornonionic fluorine-containing and/or silicon-containing surfactant can beused. Examples of such a fluorine-containing and/or silicon-containingsurfactant include the surfactants described in JP-A-62-36663,JP-A-61-226746, JP-A-61-226745, JP-A-62-170950, JP-A-63-34540,JP-A-7-230165, JP-A-8-62834, JP-A-9-54432, JP-A-9-5988 and U.S. Pat.Nos. 5,405,720, 5,360,692, 5,529,881, 5,296,330, 5,436,098, 5,576,143,5,294,511 and 5,824,451. The surfactant is preferably a nonionicsurfactant. The nonionic surfactant is not particularly limited, but afluorine-containing surfactant or a silicon-containing surfactant ismore preferred.

The amount of the surfactant used is usually from 0.001 to 5 mass %,preferably from 0.005 to 2 mass %, more preferably from 0.01 to 0.5 mass%, based on the entire amount of the developer.

After the step of performing negative tone development, a step ofstopping the development by the replacement with another solvent may bepracticed.

A step of washing the resist film with a rinsing solution containing anorganic solvent is preferably provided after the negative tonedevelopment.

A method where after washing with a rinsing solution, the rinsingsolution is removed from the substrate surface by rotating the substrateat a rotation number of 2,000 rpm to 4,000 rpm, is preferred. In thecase where the vapor pressure of the rinsing solution is low, therinsing solution remains on the substrate even after removing therinsing solution by rotating the substrate and penetrates into theresist pattern formed on the substrate to swell the resist pattern, as aresult, the dimensional uniformity of the resist pattern isdeteriorated. For this reason, the vapor pressure at 20° C. of therinsing solution is preferably 0.05 kPa or more, more preferably 0.1 kPaor more, and most preferably 0.12 kPa or more.

In the rinsing step after negative tone development, the washing ispreferably performed using a rinsing solution containing at least onekind of an organic solvent selected from an alkane-based solvent, aketone-based solvent, an ester-based solvent, an alcohol-based solvent,an amide-based solvent and an ether-based solvent. Preferably, a step ofwashing the resist film by using a rinsing solution containing at leastone kind of an organic solvent selected from a ketone-based solvent, anester-based solvent, an alcohol-based solvent and an amide-based solventis preformed after negative tone development; more preferably, a step ofwashing the resist film by using a rinsing solution containing analcohol-based solvent or an ester-based solvent is performed afternegative tone development; still more preferably, a step of washing theresist film by using a rinsing solution containing a monohydric alcoholhaving a carbon number of 6 to 8 is performed after negative tonedevelopment. The monohydric alcohol having a carbon number of 6 to 8,which is used in the rinsing step after negative tone development,includes a linear, branched or cyclic monohydric alcohol, and specificexamples of the monohydric alcohol which can be used include 1-hexanol,1-heptanol, 1-octanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol,3-heptanol, 3-octanol, 4-octanol and benzyl alcohol, with 1-hexanol,2-hexanol and 2-heptanol being preferred.

A plurality of these components may be mixed, or the solvent may be usedby mixing it with an organic solvent other than those described above.

The water content in the rinsing solution is preferably 10 mass % orless, more preferably 5 mass % or less, still more preferably 3 mass %or less. By setting the water content to 10 mass % or less, gooddevelopment characteristics can be obtained.

The rinsing solution may also be used after adding thereto a surfactantin an appropriate amount.

In the rinsing step, the wafer after negative tone development is washedusing the above-described organic solvent-containing rinsing solution.The method of washing treatment is not particularly limited but, forexample, a method of continuously ejecting the rinsing solution on asubstrate rotating at a constant speed (spin coating method), a methodof dipping the substrate in a bath filled with the rinsing solution fora fixed time (dipping method), and a method of spraying the rinsingsolution on the substrate surface (spraying method) may be applied.Above all, a method where the washing treatment is performed by the spincoating method and after the washing, the rinsing solution is removedfrom the substrate surface by rotating the substrate at a rotationnumber of 2,000 rpm to 4,000 rpm, is preferred.

As regards the development method, for example, a method of dipping thesubstrate in a bath filled with the developer for a fixed time (dippingmethod), a method of raising the developer on the substrate surface bythe effect of a surface tension and keeping it still for a fixed time,thereby performing the development (puddle method), a method of sprayingthe developer on a substrate surface (spraying method), and a method ofcontinuously ejecting the developer on the substrate rotating at aconstant speed while scanning the developer ejecting nozzle at aconstant rate (dynamic dispense method) may be applied.

In the pattern forming method of the present invention, the step offorming a film on a substrate by using a resist composition whosesolubility in a positive tone developer increases and solubility in anegative tone developer decreases upon irradiation with an actinic rayor radiation, the step of exposing the film, the step of heating thefilm, and the step of applying positive tone development to the film maybe performed by generally known methods.

The exposure apparatus for use in the present invention is not limitedin the light source wavelength, but, for example, a KrF excimer laserwavelength (248 nm), an ArF excimer laser wavelength (193 nm) and an F₂excimer laser wavelength (157 nm) can be applied.

In the step of performing exposure of the present invention, animmersion exposure method can be applied.

The immersion exposure method is a technique for raising the resolution,and this is a technique of performing the exposure by filling a highrefractive-index liquid (hereinafter sometimes referred to as an“immersion liquid”) between the projection lens and the sample.

As for the “effect of immersion”, assuming that NA₀=sin θ, theresolution and depth of focus when immersed can be expressed by thefollowing formulae:

(Resolution)=k ₁·(λ₀ /n)/NA₀

(Depth of focus)=±k ₂·(λ₀ /n)/NA₀ ²

wherein λ₀ is the wavelength of exposure light in air, n is therefractive index of the immersion liquid based on air, and θ is theconvergence half-angle of beam.

That is, the effect of immersion is equal to use of an exposurewavelength of 1/n. In other words, when the projection optical systemhas the same NA, the depth of focus can be made n times larger by theimmersion. This is effective for all pattern profiles and can becombined with the super-resolution technology under study at present,such as phase-shift method and modified illumination method.

In the case of performing immersion exposure, a step of washing the filmsurface with an aqueous chemical solution may be performed (1) beforethe exposure step after forming the film on a substrate and/or (2) afterthe step of exposing the film through an immersion liquid but before thestep of heating the film.

The immersion liquid is preferably a liquid being transparent to lightat the exposure wavelength and having as small a temperature coefficientof refractive index as possible so as to minimize the distortion of anoptical image projected on the film. Particularly, when the exposurelight source is an ArF excimer laser (wavelength: 193 nm), water ispreferably used in view of easy availability and easy handleability, inaddition to the above-described aspects.

In the case of using water, an additive (liquid) capable of decreasingthe surface tension of water and increasing the surface activity may beadded in a small ratio. This additive is preferably a liquid that doesnot dissolve the resist layer on the wafer and at the same time, givesonly a negligible effect on the optical coat at the undersurface of thelens element.

Such an additive is preferably, for example, an aliphatic alcohol havinga refractive index nearly equal to that of water, and specific examplesthereof include methyl alcohol, ethyl alcohol and isopropyl alcohol. Byvirtue of adding an alcohol having a refractive index nearly equal tothat of water, even when the alcohol component in water is evaporatedand its content concentration is changed, the change in the refractiveindex of the entire liquid can be advantageously made very small.

On the other hand, if a substance opaque to light at 193 nm or animpurity greatly differing in the refractive index from water ismingled, this incurs distortion of the optical image projected on theresist. Therefore, the water used is preferably distilled water. Purewater after further filtration through an ion exchange filter or thelike may also be used.

In the present invention, the substrate on which the film is formed isnot particularly limited, and an inorganic substrate such as silicon,SiN, SiO₂ and SiN, a coating-type inorganic substrate such as SOG, or asubstrate generally used in the process of producing a semiconductorsuch as IC or producing a circuit board of liquid crystal, thermal heador the like or in the lithography process of other photofabrications canbe used. If desired, an organic antireflection film may be formedbetween the film and the substrate.

In the present invention, the film formed on the substrate is a filmcomposed of a resist composition whose solubility in a positive tonedeveloper increases and solubility in a negative tone developerdecreases upon irradiation with an actinic ray or radiation.

The resist composition which can be used in the present invention isdescribed below.

(A) Resin Capable of Increasing the Polarity by the Action of an Acid

The resin capable of increasing the polarity by the action of an acid,which is used in the resist composition of the present invention, is aresin having a group that decomposes by the action of an acid to producean alkali-soluble group (hereinafter sometimes referred to as an“acid-decomposable group”), on either one or both of the main chain andthe side chain of the resin (sometimes referred to as an“acid-decomposable resin”, an “acid-decomposable resin (A)” or a “resin(A)). The resin is preferably a resin whose solubility in a positivetone developer increases and which has a monocyclic or polycyclicalicyclic hydrocarbon structure and can increase the porality, increasethe solubility in an alkali developer and decrease the solubility in anorganic solvent by the action of an acid (hereinafter sometimes referredto as an “alicyclic hydrocarbon-based acid-decomposable resin”).Because, the polarity of the resin is greatly changed between before andafter irradiation of an actinic ray or radiation and when the resistfilm is developed using a positive tone developer (preferably an alkalideveloper) and a negative tone developer (preferably an organicsolvent), the dissolution contrast rises. Furthermore, the resin havinga monocyclic or polycyclic alicyclic hydrocarbon structure generally hashigh hydrophobicity and ensures a high development rate at the time ofdeveloping the resist film in the region of weak light irradiationintensity with a negative tone developer (preferably an organicdeveloper), and the developability in using a negative tone developer isenhanced.

The group capable of decomposing by the action of an acid(acid-decomposable groups) is preferably a group obtained bysubstituting the hydrogen atom of an alkali-soluble group with a groupcapable of leaving by the action of an acid.

Examples of the alkali-soluble group include groups having a phenolichydroxyl group, a carboxylic acid group, a fluorinated alcohol group, asulfonic acid group, a sulfonamide group, a sulfonylimide group, an(alkylsulfonyl)(alkylcarbonyl)methylene group, an(alkylsulfonyl)(alkylcarbonyl)imide group, a bis(alkylcarbonyl)methylenegroup, a bis(alkylcarbonyl)imide group, a bis(alkylsulfonyl)methylenegroup, a bis(alkylsulfonyl)imide group, a tris(alkylcarbonyl)methylenegroup or a tris(alkylsulfonyl)methylene group.

The alkali-soluble group is preferably a carboxylic acid group, afluorinated alcohol group (preferably hexafluoroisopropanol) or asulfonic acid group.

Examples of the group capable of leaving by the action of an acidinclude —C(R₃₆)(R₃₇)(R₃₈), —C(R₃₆)(R₃₇)(OR₃₉) and —C(R₀₁)(R₀₂)(OR₃₉).

In the formulae, each of R₃₆ to R₃₉ independently represents an alkylgroup, a cycloalkyl group, an aryl group, an aralkyl group or an alkenylgroup. R₃₆ and R₃₇ may combine with each other to form a ring.

Each of R₀₁ and R₀₂ independently represents a hydrogen atom, an alkylgroup, a cycloalkyl group, an aryl group, an aralkyl group or an alkenylgroup.

The acid-decomposable group is preferably a cumyl ester group, an enolester group, an acetal ester group, a tertiary alkyl ester group or thelike, more preferably a tertiary alkyl ester group.

The resist composition of the present invention containing a resin (A)having a monocyclic or polycyclic alicyclic hydrocarbon structure andbeing capable of increasing the polarity by the action of an acid can besuitably used when ArF excimer laser light is irradiated.

The resin having a monocyclic or polycyclic alicyclic hydrocarbonstructure and being capable of increasing the polarity by the action ofan acid (hereinafter sometimes referred to as an “alicyclichydrocarbon-based acid-decomposable resin”) is preferably a resincontaining at least one member selected from the group consisting of arepeating unit having an alicyclic hydrocarbon-containing partialstructure represented by any one of the following formulae (pI) to (pV)and a repeating unit represented by the following formula (II-AB).

In formulae (pI) to (pV), R₁₁ represents a methyl group, an ethyl group,an n-propyl group, an isopropyl group, an n-butyl group, an isobutylgroup or a sec-butyl group.

Z represents an atomic group necessary for forming a cycloalkyl grouptogether with the carbon atom.

Each of R₁₂ to R₁₆ independently represents a linear or branched alkylgroup having a carbon number of 1 to 4 or a cycloalkyl group, providedthat at least one of R₁₂ to R₁₄ or either one of R₁₅ and R₁₆ representsa cycloalkyl group.

Each of R₁₇ to R₂₁ independently represents a hydrogen atom, a linear orbranched alkyl group having a carbon number of 1 to 4 or a cycloalkylgroup, provided that at least one of R₁₇ to R₂₁ represents a cycloalkylgroup and that either one of R₁₉ and R₂₁ represents a linear or branchedalkyl group having a carbon number of 1 to 4 or a cycloalkyl group.

Each of R₂₂ to R₂₅ independently represents a hydrogen atom, a linear orbranched alkyl group having a carbon number of 1 to 4 or a cycloalkylgroup, provided that at least one of R₂₂ to R₂₅ represents a cycloalkylgroup. R₂₃ and R₂₄ may combine with each other to form a ring.

In formula (II-AB), each of R₁₁′ and R₁₂′ independently represents ahydrogen atom, a cyano group, a halogen atom or an alkyl group.

Z′ represents an atomic group for forming an alicyclic structurecontaining two bonded carbon atoms (C—C).

Formula (II-AB) is preferably the following formula (II-AB1) or(II-AB2):

In formulae (II-AB1) and (II-AB2), each of R₁₃′ to R₁₆′ independentlyrepresents a hydrogen atom, a halogen atom, a cyano group, —COOH,—COOR₅, a group capable of decomposing by the action of an acid,—C(═O)—X-A′—R₁₇′, an alkyl group or a cycloalkyl group, and at least twomembers out of R₁₃′ to R₁₆′ may combine to form a ring.

R₅ represents an alkyl group, a cycloalkyl group or a group having alactone structure.

X represents an oxygen atom, a sulfur atom, —NH—, —NHSO₂— or —NHSO₂NH—.

A′ represents a single bond or a divalent linking group.

R₁₇′ represents —COOH, —COOR₅, —CN, a hydroxyl group, an alkoxy group,—CO—NH—R₆, —CO—NH—SO₂—R₆ or a group having a lactone structure.

R₆ represents an alkyl group or a cycloalkyl group.

n represents 0 or 1.

In formulae (pI) to (pV), the alkyl group of R₁₂ to R₂₅ is a linear orbranched alkyl group having a carbon number of 1 to 4.

The cycloalkyl group of R₁₁ to R₂₅ and the cycloalkyl group formed by Ztogether with the carbon atom may be monocyclic or polycyclic. Specificexamples thereof include a group having a carbon number of 5 or more andhaving a monocyclo, bicyclo, tricyclo or tetracyclo structure or thelike. The carbon number thereof is preferably from 6 to 30, morepreferably from 7 to 25. These cycloalkyl groups each may have asubstituent.

Preferred examples of the cycloalkyl group include an adamantyl group, anoradamantyl group, a decalin residue, a tricyclodecanyl group, atetracyclododecanyl group, a norbornyl group, a cedrol group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctylgroup, a cyclodecanyl group and a cyclododecanyl group. Among these,more preferred are an adamantyl group, a norbornyl group, a cyclohexylgroup, a cyclopentyl group, a tetracyclododecanyl group and atricyclodecanyl group.

Examples of the substituent which the alkyl group and cycloalkyl groupeach may further have include an alkyl group (having a carbon number of1 to 4), a halogen atom, a hydroxyl group, an alkoxy group (having acarbon number of 1 to 4), a carboxyl group and an alkoxycarbonyl group(having a carbon number of 2 to 6). Examples of the substituent whichthese alkyl group, alkoxy group, alkoxycarbonyl group and the like eachmay further have include a hydroxyl group, a halogen atom and an alkoxygroup.

The structures represented by formulae (pI) to (pV) each can be used forthe protection of an alkali-soluble group in the resin. Examples of thealkali-soluble group include various groups known in this technicalfield.

Specific examples thereof include a structure where the hydrogen atom ofa carboxylic acid group, a sulfonic acid group, a phenol group or athiol group is replaced by the structure represented by any one offormulae (pI) to (pV). Among these, preferred is a structure where thehydrogen atom of a carboxylic acid group or a sulfonic acid group isreplaced by the structure represented by any one of formulae (pI) to(pV).

The repeating unit having an alkali-soluble group protected by thestructure represented by any one of formulae (pI) to (pV) is preferablya repeating unit represented by the following formula (pA):

In the formula, R represents a hydrogen atom, a halogen atom or a linearor branched alkyl group having a carbon number of 1 to 4, and aplurality of R's may be the same or different from each other.

A represents a single bond, or a sole group or a combination of two ormore groups selected from the group consisting of an alkylene group, anether group, a thioether group, a carbonyl group, an ester group, anamido group, a sulfonamido group, a urethane group and a ureylene group,and is preferably a single bond.

Rp₁ represents a group represented by any one of formulae (pI) to (pV).

The repeating unit represented by formula (pA) is more preferably arepeating unit composed of a 2-alkyl-2-adamantyl (meth)acrylate or adialkyl(1-adamantyl)methyl (meth)acrylate.

Specific examples of the repeating unit having an acid-decomposablegroup are set forth below, but the present invention is not limitedthereto.

(In the formulae, Rx represents H, CH₃ or CH₂OH, and each of Rxa and Rxbindependently represents an alkyl group having a carbon number of 1 to4.)

Examples of the halogen atom of R₁₁′ and R₁₂′ in formula (II-AB) includea chlorine atom, a bromine atom, a fluorine atom and an iodine atom.

The alkyl group of R₁₁′ and R₁₂′ includes a linear or branched alkylgroup having a carbon number of 1 to 10.

The atomic group of Z′ for forming an alicyclic structure is an atomicgroup for forming, in the resin, a repeating unit composed of analicyclic hydrocarbon which may have a substituent. Above all, an atomicgroup for forming a crosslinked alicyclic structure to form acrosslinked alicyclic hydrocarbon repeating unit is preferred.

Examples of the skeleton of the alicyclic hydrocarbon formed are thesame as those of the alicyclic hydrocarbon group of R₁₂ to R₂₅ informulae (pI) to (pV).

The skeleton of the alicyclic hydrocarbon may have a substituent, andexamples of the substituent include R₁₃′ to R₁₆′ in formulae (II-AB1)and (II-AB2).

In the alicyclic hydrocarbon-based acid-decomposable resin for use inthe present invention, the group capable of decomposing by the action ofan acid may be contained in at least one repeating unit out of therepeating unit having an alicyclic hydrocarbon-containing partialstructure represented by any one of formulae (pI) to (pV), the repeatingunit represented by formula (II-AB), and the repeating unit composed ofa copolymerization component described later. The group capable ofdecomposing by the action of an acid is preferably contained in therepeating unit having an alicylcic hydrocarbon-containing partialstructure represented by any one of formulae (pI) to (pV).

Various substituents R₁₃′ to R₁₆′ in formulae (II-AB1) and (II-AB2) maybecome substituents of the atomic group Z′ for forming an alicyclicstructure or the atomic group Z′ for forming a crosslinked alicyclicstructure in formula (II-AB).

Specific examples of the repeating units represented by formulae(II-AB1) and (II-AB2) are set forth below, but the present invention isnot limited to these specific examples.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention preferably has a lactone group. As for the lactonegroup, any group may be used as long as it has a lactone structure, buta group having a 5- to 7-membered ring lactone structure is preferred.The 5- to 7-membered ring lactone structure is preferably condensed withanother ring structure in the form of forming a bicyclo or spirostructure. The resin more preferably has a repeating unit containing agroup having a lactone structure represented by any one of the followingformulae (LC1-1) to (LC1-16). The group having a lactone structure maybe bonded directly to the main chain. Among these lactone structures,preferred are groups represented by formulae (LC1-1), (LC1-4), (LC1-5),(LC1-6), (LC1-13) and (LC1-14). By virtue of using a specific lactonestructure, the line edge roughness and development defect are improved.

The lactone structure moiety may or may not have a substituent (Rb₂).Preferred examples of the substituent (Rb₂) include an alkyl grouphaving a carbon number of 1 to 8, a cycloalkyl group having a carbonnumber of 4 to 7, an alkoxy group having a carbon number of 1 to 8, analkoxycarbonyl group having a carbon number of 2 to 8, a carboxyl group,a halogen atom, a hydroxyl group, a cyano group and an acid-decomposablegroup. n₂ represents an integer of 0 to 4. When n2 is an integer of 2 ormore, each Rb₂ may be the same as or different from every other Rb₂ andalso, the plurality of substituents (Rb₂) may combine with each other toform a ring.

Examples of the repeating unit containing a group having a lactonestructure represented by any one of formulae (LC1-1) to (LC1-16) includea repeating unit where at least one of R₁₃′ to R₁₆′ in formula (II-AB1)or (II-AB2) has a group represented by any one of formulae (LC1-1) to(LC1-16) (for example, R₅ of —COOR₅ is a group represented by any one offormulae (LC1-1) to (LC1-16)), and a repeating unit represented by thefollowing formula (AI):

In formula (AI), Rb₀ represents a hydrogen atom, a halogen atom or analkyl group having a carbon number of 1 to 4.

Preferred examples of the substituent which the alkyl group of Rb₀ mayhave include a hydroxyl group and a halogen atom.

The halogen atom of Rb₀ includes a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Rb₀ is preferably a hydrogen atom, a methyl group, a hydroxymethyl groupor a trifluoromethyl group, particularly preferably a hydrogen atom or amethyl group.

Ab represents a single bond, an alkylene group, a divalent linking grouphaving a monocyclic or polycyclic alicyclic hydrocarbon structure, anether group, an ester group, a carbonyl group, or a divalent groupformed by combining these groups and is preferably a single bond or alinking group represented by -Abl-CO₂—. Ab₁ represents a linear orbranched alkylene group or a monocyclic or polycyclic cycloalkylenegroup and is preferably a methylene group, an ethylene group, acyclohexylene group, an adamantylene group or a norbornylene group.

V represents a group represented by any one of formulae (LC1-1) to(LC1-16).

The repeating unit having a lactone structure usually has an opticalisomer, but any optical isomer may be used. One optical isomer may beused alone or a mixture of a plurality of optical isomers may be used.In the case of mainly using one optical isomer, the optical purity (ee)thereof is preferably 90 or more, more preferably 95 or more.

Specific examples of the repeating unit having a lactone structure areset forth below, but the present invention is not limited thereto.

(In the formulae, Rx is H, CH₃, CH₂OH or CF₃.)

(In the formulae, Rx is H, CH₃, CH₂OH or CF₃.)

(In the formulae, Rx is H, CH₃, CH₂OH or CF₃.)

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention preferably has a repeating unit containing an organicgroup having a polar group, more preferably a repeating unit having analicyclic hydrocarbon structure substituted by a polar group. By virtueof this repeating unit, the adherence to substrate and the affinity fordeveloper are enhanced. The alicyclic hydrocarbon structure of the polargroup-substituted alicyclic hydrocarbon structure is preferably anadamantyl group, a diamantyl group or a norbornane group. The polargroup is preferably a hydroxyl group or a cyano group.

The polar group-substituted alicyclic hydrocarbon structure ispreferably a partial structure represented by the following formulae(VIIa) to (VIId):

In formulae (VIIa) to (VIIc), each of R_(2c) to R_(4c) independentlyrepresents a hydrogen atom, a hydroxyl group or a cyano group, providedthat at least one of R_(2c) to R_(4c) represents a hydroxyl group or acyano group. A structure where one or two members out of R_(2c) toR_(4c) are a hydroxyl group with the remaining being a hydrogen atom ispreferred.

In formula (VIIa), it is more preferred that two members out of R_(2c)to R_(4c) are a hydroxyl group and the remaining is a hydrogen atom.

The repeating unit having a group represented by any one of formulae(VIIa) to (VIId) includes a repeating unit where at least one of R₁₃′ toR₁₆′ in formula (II-AB1) or (II-AB2) has a group represented by any oneof formulae (VIIa) to (VIId) (for example, R₅ of —COOR₅ is a grouprepresented by any one of formulae (VIIa) to (VIId)), and repeatingunits represented by the following formulae (AIIa) to (AIId):

In formulae (AIIa) to (AIId), R_(1c) represents a hydrogen atom, amethyl group, a trifluoromethyl group or a hydroxymethyl group.

R_(2c) to R_(4c) have the same meanings as R_(2c) to R_(4c) in formulae(VIIa) to (VIIc).

Specific examples of the repeating unit having a structure representedby any one of formulae (AIIa) to (AIId) are set forth below, but thepresent invention is not limited thereto.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention may contain a repeating unit represented by thefollowing formula (VIII):

In formula (VIII), Z₂ represents —O— or —N(R₄₁)—. R₄₁ represents ahydrogen atom, a hydroxyl group, an alkyl group or —OSO₂—R₄₂. R₄₂represents an alkyl group, a cycloalkyl group or a camphor residue. Thealkyl group of R₄₁ and R₄₂ may be substituted by a halogen atom(preferably fluorine atom) or the like.

Specific examples of the repeating unit represented by formula (VIII)are set forth below, but the present invention is not limited thereto.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention preferably contains a repeating unit having analkali-soluble group, more preferably a repeating unit having a carboxylgroup. By virtue of containing this repeating unit, the resolutionincreases in the usage of forming contact holes. As for the repeatingunit having a carboxyl group, a repeating unit where a carboxyl group isdirectly bonded to the resin main chain, such as repeating unit by anacrylic acid or a methacrylic acid, a repeating unit where a carboxylgroup is bonded to the resin main chain through a linking group, and arepeating unit where a carboxyl group is introduced into the terminal ofthe polymer chain by using a polymerization initiator or chain transferagent having an alkali-soluble group at the polymerization, all arepreferred. The linking group may have a monocyclic or polycyclichydrocarbon structure. A repeating unit by an acrylic acid or amethacrylic acid is more preferred.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention may further contain a repeating unit having from 1 to3 groups represented by formula (F1). Thanks to this repeating unit, theperformance in terms of line edge roughness is enhanced.

In formula (F1), each of R₅₀ to R₅₅ independently represents a hydrogenatom, a fluorine atom or an alkyl group, provided that at least one ofR₅₀ to R₅₅ is a fluorine atom or an alkyl group with at least onehydrogen atom being substituted by a fluorine atom.

Rx represents a hydrogen atom or an organic group (preferably anacid-decomposable protective group, an alkyl group, a cycloalkyl group,an acyl group or an alkoxycarbonyl group).

The alkyl group of R₅₀ to R₅₅ may be substituted by a halogen atom(e.g., fluorine), a cyano group or the like, and the alkyl group ispreferably an alkyl group having a carbon number of 1 to 3, such asmethyl group and trifluoromethyl group.

It is preferred that R₅₀ to R₅₅ all are a fluorine atom.

The organic group represented by Rx is preferably an acid-decomposableprotective group, an alkyl group, a cycloalkyl group, an acyl group, analkylcarbonyl group, an alkoxycarbonyl group, an alkoxycarbonylmethylgroup, an alkoxymethyl group or a 1-alkoxyethyl group, each of which mayhave a substituent.

The repeating unit having a group represented by formula (F1) ispreferably a repeating unit represented by the following formula (F2):

In formula (F2), Rx represents a hydrogen atom, a halogen atom or analkyl group having a carbon number of 1 to 4. Preferred examples of thesubstituent which the alkyl group of Rx may have include a hydroxylgroup and a halogen atom.

Fa represents a single bond or a linear or branched alkylene group andis preferably a single bond.

Fb represents a monocyclic or polycyclic hydrocarbon group.

Fc represents a single bond or a linear or branched alkylene group andis preferably a single bond or a methylene group.

F₁ represents a group represented by formula (F1).

p₁ represents a number of 1 to 3.

The cyclic hydrocarbon group in Fb is preferably a cyclopentyl group, acyclohexyl group or a norbornyl group.

Specific examples of the repeating unit having a group represented byformula (F1) are set forth below, but the present invention is notlimited thereto.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention may further contain a repeating unit having analicyclic hydrocarbon structure and not exhibiting acid decomposability.Thanks to this repeating unit, the dissolving out of low molecularcomponents from the resist film to the immersion liquid at the immersionexposure can be reduced. Examples of this repeating unit include1-adamantyl (meth)acrylate, tricyclodecanyl (meth)acrylate andcyclohexyl (meth)acrylate.

As a repeating unit having an alicyclic hydrocarbon structure and notexhibiting acid decomposability, for example, a repeating unit havingneither a hydroxyl group nor a cyano group is exemplified, and arepeating unit represented by formula (IX) is preferred:

In formula (IX), R₅ represents a hydrocarbon group having at least onecyclic structure and having neither a hydroxyl group nor a cyano group.

Ra represents a hydrogen atom, an alkyl group or a —CH₂—O—Ra₂ group,wherein Ra₂ represents a hydrogen atom, an alkyl group or an acyl group.Ra is preferably a hydrogen atom, a methyl group, a hydroxymethyl groupor a trifluoromethyl group, particularly preferably a hydrogen atom or amethyl group.

The cyclic structure possessed by R₅ includes a monocyclic hydrocarbongroup and a polycyclic hydrocarbon group. Examples of the monocyclichydrocarbon group include a cycloalkyl group having a carbon number of 3to 12, such as cyclopentyl group, cyclohexyl group, cycloheptyl groupand cyclooctyl group, and a cycloalkenyl group having a carbon number of3 to 12, such as cyclohexenyl group. As the monocyclic hydrocarbongroup, a monocyclic hydrocarbon group having a carbon number of 3 to 7is preferred, and a cyclopentyl group and a cyclohexyl group are morepreferred.

The polycyclic hydrocarbon group includes a ring gathered hydrocarbongroup and a crosslinked cyclic hydrocarbon group. Examples of the ringgathered hydrocarbon group include a bicyclohexyl group and aperhydronaphthalenyl group. Examples of the crosslinked cyclichydrocarbon ring include a bicyclic hydrocarbon ring such as pinane,bomane, norpinane, norbornane and bicyclooctane rings (e.g.,bicyclo[2.2.2]octane ring, bicyclo[3.2.1]octane ring), a tricyclichydrocarbon ring such as homobredane, adamantane,tricyclo[5.2.1.0^(2,6)]decane and tricyclo[4.3.1.1^(2,5)]undecane rings,and a tetracyclic hydrocarbon ring such astetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecane andperhydro-1,4-methano-5,8-methanonaphthalene rings. The crosslinkedcyclic hydrocarbon ring also includes a condensed cyclic hydrocarbonring, and examples thereof include a condensed ring formed by condensinga plurality of 5- to 8-membered cycloalkane rings such asperhydronaphthalene (decalin), perhydroanthracene, perhydrophenanthrene,perhydroacenaphthene, perhydrofluorene, perhydroindene andperhydrophenanthrene rings.

As the crosslinked cyclic hydrocarbon ring, a norbornyl group, anadamantyl group, a bicyclooctanyl group, atricyclo[5.2.1.0^(2.6)]decanyl group are preferred, and a norbornylgroup and an adamantyl group are more preferred.

Such an alicyclic hydrocarbon group may have a substituent, andpreferred examples of the substituent include a halogen atom, an alkylgroup, a hydroxyl group protected by a protective group, and an aminogroup protected by a protective group. Preferred halogen atoms includebromine, chlorine and fluorine atoms, and preferred alkyl groups includemethyl, ethyl, butyl and tert-butyl groups. This alkyl group may furtherhave a substituent, and the substituent which the alkyl group mayfurther have includes a halogen atom, an alkyl group, a hydroxyl groupprotected by a protective group, and an amino group protected by aprotective group.

Examples of the protective group include an alkyl group, a cycloalkylgroup, an aralkyl group, a substituted methyl group, a substituted ethylgroup, an acyl group, an alkoxycarbonyl group and an aralkyloxycarbonylgroup. For example, the alkyl group is preferably an alkyl group havinga carbon number of 1 to 4, the substituted methyl group is preferably amethoxymethyl, methoxythiomethyl, benzyloxymethyl, tert-butoxymethyl or2-methoxyethoxymethyl group, the substituted ethyl group is preferably a1-ethoxyethyl or 1-methyl-1-methoxyethyl group, the acyl group ispreferably an aliphatic acyl group having a carbon number of 1 to 6,such as formyl, acetyl, propionyl, butyryl, isobutyryl, valeryl andpivaloyl groups, and the alkoxycarbonyl group is preferably analkoxycarbonyl group having a carbon number of 1 to 4.

The content of the repeating unit represented by formula (IX) havingneither a hydroxyl group nor a cyano group is preferably from 0 to 40mol %, more preferably from 0 to 20 mol %, based on all repeating unitsin the alicyclic hydrocarbon-based acid-decomposable resin.

Specific examples of the repeating unit represented by formula (IX) areset forth below, but the present invention is not limited thereto.

In formulae, Ra represents H, CH₃, CH₂OH or CF₃.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention may contain, in addition to the above-describedrepeating units, various repeating structural units for the purpose ofcontrolling dry etching resistance, suitability for standard developer,adherence to substrate, resist profile and properties generally requiredof the resist, such as resolution, heat resistance and sensitivity.

Examples of such a repeating structural unit include, but are notlimited to, repeating structural units corresponding to the monomersdescribed below.

Thanks to such a repeating structural unit, the performance required ofthe alicyclic hydrocarbon-based acid-decomposable resin, particularly,(1) solubility in coating solvent, (2) film-forming property (glasstransition point), (3) solubility in positive or negative tonedeveloper, (4) film loss (selection of hydrophilic, hydrophobic andalkali-soluble group), (5) adherence of unexposed area to substrate, (6)dry etching resistance, and the like, can be subtly controlled.

Examples of the monomer include a compound having oneaddition-polymerizable unsaturated bond selected from acrylic acidesters, methacrylic acid esters, acrylamides, methacrylamides, allylcompounds, vinyl ethers and vinyl esters.

Other than these, an addition-polymerizable unsaturated compoundcopolymerizable with the monomers corresponding to the above-describedvarious repeating structural units may be copolymerized.

In the alicyclic hydrocarbon-based acid-decomposable resin, the molarratio of respective repeating structural units contained isappropriately determined to control the dry etching resistance ofresist, suitability for standard developer, adherence to substrate,resist profile and performances generally required of the resist, suchas resolution, heat resistance and sensitivity.

The preferred embodiment of the alicyclic hydrocarbon-basedacid-decomposable resin for use in the present invention includes thefollowings:

(1) a resin containing a repeating unit having an alicyclichydrocarbon-containing partial structure represented by any one offormulae (pI) to (pV) (side chain type), preferably a resin containing a(meth)acrylate repeating unit having a structure represented by any oneof formulae (pI) to (pV), and

(2) a resin containing a repeating unit represented by formula (II-AB)(main chain type).

The resin of (2) further includes:

(3) a resin having a repeating unit represented by formula (II-AB), amaleic anhydride derivative and a (meth)acrylate structure (hybridtype).

In the alicyclic hydrocarbon-based acid-decomposable resin, the contentof the repeating unit having an acid-decomposable group is preferablyfrom 10 to 60 mol %, more preferably from 20 to 50 mol %, still morepreferably from 30 to 50 mol %, based on all repeating structural units.

In the alicyclic hydrocarbon-based acid-decomposable resin, the contentof the repeating unit having an alicyclic hydrocarbon-containing partialstructure represented by any one of formulae (pI) to (pV) is preferablyfrom 20 to 70 mol %, more preferably from 20 to 50 mol %, still morepreferably from 30 to 50 mol %, based on all repeating structural units.

In the alicyclic hydrocarbon-based acid-decomposable resin, the contentof the repeating unit represented by formula (II-AB) is preferably from10 to 60 mol %, more preferably from 15 to 55 mol %, still morepreferably from 20 to 50 mol %, based on all repeating structural units.

In the acid-decomposable resin, the content of the repeating unit havinga lactone ring is preferably from 10 to 70 mol %, more preferably from20 to 60 mol %, still more preferably from 25 to 50 mol %, based on allrepeating structural units.

In the acid-decomposable resin, the content of the repeating unit havinga polar group-containing organic group is preferably from 1 to 40 mol %,more preferably from 5 to 30 mol %, still more preferably from 5 to 20mol %, based on all repeating structural units.

The content of the repeating structural unit based on the monomer as thefurther copolymerization component in the resin can also beappropriately selected according to the desired resist performance butin general, the content thereof is preferably 99 mol % or less, morepreferably 90 mol % or less, still more preferably 80 mol % or less,based on the total molar number of the repeating structural unit havingan alicyclic hydrocarbon-containing partial structure represented by anyone of formulae (pI) to (pV) and the repeating unit represented byformula (II-AB).

In the case of using the resist composition of the present invention forArF exposure, the acid-decomposable resin (A) preferably has no aromaticgroup in view of transparency to ArF light.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention is preferably a resin where all repeating units arecomposed of a (meth)acrylate-based repeating unit. In this case, therepeating units may be all a methacrylate-based repeating unit, all anacrylate-based repeating unit, or all a mixture of methacrylate-basedrepeating unit/acrylate-based repeating unit, but the acrylate-basedrepeating unit preferably accounts for 50 mol % or less of all repeatingunits.

The alicyclic hydrocarbon-based acid-decomposable resin is preferably acopolymer having at least three kinds of repeating units, that is, a(meth)acrylate-based repeating unit having a lactone ring, a(meth)acrylate-based repeating unit having an organic group substitutedby at least either a hydroxyl group or a cyano group, and a(meth)acrylate-based repeating unit having an acid-decomposable group.

The copolymer is preferably a ternary copolymerization polymercontaining from 20 to 50 mol % of the repeating unit having an alicyclichydrocarbon-containing partial structure represented by any one offormulae (pI) to (pV), from 20 to 50 mol % of the repeating unit havinga lactone structure and from 5 to 30 mol % of the repeating unit havinga polar group-substituted alicyclic hydrocarbon structure, or aquaternary copolymerization polymer further containing from 0 to 20 mol% of other repeating units.

In particular, the resin is preferably a ternary copolymerizationpolymer containing from 20 to 50 mol % of an acid-decomposablegroup-containing repeating unit represented by any one of the followingformulae (ARA-1) to (ARA-5), from 20 to 50 mol % of a lactonegroup-containing repeating unit represented by any one of the followingformulae (ARL-1) to (ARL-6), and from 5 to 30 mol % of a repeating unithaving a polar group-substituted alicyclic hydrocarbon structurerepresented by any one of the following formulae (ARH-1) to (ARH-3), ora quaternary copolymerization polymer further containing from 5 to 20mol % of a repeating unit having a carboxyl group or a structurerepresented by formula (F1) and a repeating unit having an alicyclichydrocarbon structure and not exhibiting acid decomposability.

(In the formulae, Rxy₁ represents a hydrogen atom or a methyl group, andRxa₁ and Rxb₁ each represents a methyl group or an ethyl group).

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention can be synthesized by an ordinary method (for example,radical polymerization). Examples of the synthesis method in generalinclude a batch polymerization method of dissolving the monomer speciesand an initiator in a solvent and heating the solution, therebyeffecting the polymerization, and a dropping polymerization method ofadding dropwise a solution containing monomer species and an initiatorto a heated solvent over 1 to 10 hours. A dropping polymerization methodis preferred. Examples of the reaction solvent include tetrahydrofuran,1,4-dioxane, ethers such as diisopropyl ether, ketones such as methylethyl ketone and methyl isobutyl ketone, an ester solvent such as ethylacetate, an amide solvent such as dimethylformamide anddimethylacetamide, and the later-described solvent capable of dissolvingthe composition of the present invention, such as propylene glycolmonomethyl ether acetate, propylene glycol monomethyl ether andcyclohexanone. The polymerization is more preferably performed using thesame solvent as the solvent used in the resist composition of thepresent invention. By the use of this solvent, production of particlesduring storage can be suppressed.

The polymerization reaction is preferably performed in an inert gasatmosphere such as nitrogen and argon. As for the polymerizationinitiator, the polymerization is started using a commercially availableradical initiator (e.g., azo-based initiator, peroxide). The radicalinitiator is preferably an azo-based initiator, and an azo-basedinitiator having an ester group, a cyano group or a carboxyl group ispreferred. Preferred examples of the initiator includeazobisisobutyronitrile, azobisdimethylvaleronitrile and dimethyl2,2′-azobis(2-methylpropionate). The initiator is added additionally orin parts, if desired. After the completion of reaction, the reactionproduct is charged into a solvent, and the desired polymer is recoveredby a method such as powder or solid recovery. The reaction concentrationis from 5 to 50 mass %, preferably from 10 to 30 mass %.

The reaction temperature is usually from 10 to 150° C., preferably from30 to 120° C., more preferably from 60 to 100° C.

The purification may be performed by the same method as that for theresin (D) described later, and a normal method, for example, aliquid-liquid extraction method of combining water washing with anappropriate solvent to remove residual monomers or oligomer components,a purification method in a solution sate, such as ultrafiltration ofextracting and removing only polymers having a molecular weight lowerthan a specific molecular weight, a reprecipitation method of addingdropwise the resin solution in a poor solvent to solidify the resin inthe poor solvent and thereby remove residual monomers and the like, or apurification method in a solid state, such as washing of the resinslurry with a poor solvent after separation by filtration, may beemployed.

The weight average molecular weight of the resin for use in the presentinvention is preferably 6,000 or less, more preferably from 1,000 to5,000, still more preferably from 2,000 to 3,500, in terms ofpolystyrene by the GPC method. When the weight average molecular weightof the resin is 6,000 or less, the line edge roughness of the resistpattern is reduced.

The dispersity (molecular weight distribution, Mw/Mn) is preferably 1.7or less, more preferably 1.5 or less, still more preferably 1.3 or less.As the dispersity is smaller, the line edge roughness of the resistpattern is more reduced.

To speak in more detail, the resin for use in the present invention is(a1) a resin having an alicyclic hydrocarbon structure and a dispersityof 1.7 or less and being capable of increasing the polarity by theaction of an acid, or (a2) a resin having an alicyclic hydrocarbonstructure and a weight average molecular weight of 6,000 or less andbeing capable of increasing the polarity by the action of an acid,preferably (a3) a resin having an alicyclic hydrocarbon structure, adispersity of 1.7 or less and a weight average molecular weight of 6,000or less and being capable of increasing the polarity by the action of anacid.

The molecular weight can be controlled by adjusting the amount added ofthe radical initiator, and as the amount added of the initiator materialis larger, the molecular weight becomes smaller. As for the control ofdispersity, a living polymerization method or the like disclosed inJP-A-2004-220009 may be used, and in addition, the dispersity can alsobe reduced by raising the proportion of the good solvent for the resinduring precipitation when synthesizing the resin.

In the resin for use in the present invention, by combining the weightaverage molecular weight and the dispersity in respective preferredranges, the line edge roughness can be more reduced.

In the resist composition of the present invention, the amount of allresins for use in the present invention blended in the entirecomposition is preferably from 50 to 99.9 mass %, more preferably from60 to 99.0 mass %, based on the entire solid content.

In the present invention, one kind of a resin may be used or a pluralityof kinds of resins may be used in combination.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention preferably contains no fluorine or silicon atom inview of compatibility with the resin (D).

(B) Compound Capable of Generating an Acid Upon Irradiation with anActinic Ray or Radiation

The resist composition of the present invention contains a compoundcapable of generating an acid upon irradiation with an actinic ray orradiation (sometimes referred to as a “photo-acid generator” or“component (B)”).

The photo-acid generator which can be used may be appropriately selectedfrom a photo-initiator for cationic photopolymerization, aphoto-initiator for radical photopolymerization, a photodecoloring agentfor dyes, a photodiscoloring agent, a known compound used formicroresist or the like and capable of generating an acid uponirradiation with an actinic ray or radiation, and a mixture thereof.

Examples thereof include a diazonium salt, a phosphonium salt, asulfonium salt, an iodonium salt, an imidosulfonate, an oxime sulfonate,a diazodisulfone, a disulfone and an o-nitrobenzyl sulfonate.

Also, a compound where such a group or compound capable of generating anacid upon irradiation with an actinic ray or radiation is introducedinto the main or side chain of the polymer, for example, compoundsdescribed in U.S. Pat. No. 3,849,137, German Patent 3,914,407,JP-A-63-26653, JP-A-55-164824, JP-A-62-69263, JP-A-63-146038,JP-A-63-163452, JP-A-62-153853 and JP-A-63-146029, may be used.

Furthermore, compounds capable of generating an acid by the effect oflight described, for example, in U.S. Pat. No. 3,779,778 and EuropeanPatent 126,712 may also be used.

Out of the compounds capable of generating an acid upon irradiation withan actinic ray or radiation, preferred are the compounds represented bythe following formulae (ZI), (ZII) and (ZIII):

In formula (ZI), each of R₂₀₁, R₂₀₂ and R₂₀₃ independently represents anorganic group.

X⁻ represents a non-nucleophilic anion, and preferred examples thereofinclude sulfonate anion, carboxylate anion, bis(alkylsulfonyl)amideanion, tris(alkylsulfonyl)methide anion, BF₄ ⁻, PF₆ ⁻ and SbF₆ ⁻. Theanion is preferably an organic anion containing a carbon atom.

The preferred organic anion includes organic anions represented by thefollowing formulae:

In the formulae, Rc₁ represents an organic group.

The organic group of Rc₁ includes an organic group having a carbonnumber of 1 to 30, and preferred examples thereof include an alkyl groupwhich may be substituted, an aryl group which may be substituted, and agroup where a plurality of these groups are connected through a singlebond or a linking group such as —O—, —CO₂—, —S—, —SO₃— and —SO₂N(Rd₁)—.Rd₁ represents a hydrogen atom or an alkyl group.

Each of Rc₃, Rc₄ and Rc₅ independently represents an organic group.Preferred organic groups of Rc₃, Rc₄ and Rc₅ are the same as preferredorganic groups in Rc₁. The organic group is most preferably aperfluoroalkyl group having a carbon number of 1 to 4.

Rc₃ and Rc₄ may combine to form a ring. The group formed by combiningRc₃ and Rc₄ includes an alkylene group and an arylene group, and aperfluoroalkylene group having a carbon number of 2 to 4 is preferred.

The organic group of Rc₁ and Rc₃ to Rc₅ is particularly preferably analkyl group with the 1-position being substituted by a fluorine atom ora fluoroalkyl group, or a phenyl group substituted by a fluorine atom ora fluoroalkyl group. By virtue of having a fluorine atom or afluoroalkyl group, the acidity of the acid generated upon irradiationwith light is raised and the sensitivity is enhanced. Also, when Rc₃ andRc₄ are combined to form a ring, the acidity of the acid generated uponirradiation with light is raised and the sensitivity is enhanced.

The carbon number of the organic group as R₂₀₁, R₂₀₂ and R₂₀₃ isgenerally from 1 to 30, preferably from 1 to 20.

Two members out of R₂₀₁ to R₂₀₃ may combine to form a ring structure,and the ring may contain an oxygen atom, a sulfur atom, an ester bond,an amide bond or a carbonyl group. Examples of the group formed bycombining two members out of R₂₀₁ to R₂₀₃ include an alkylene group(e.g., butylene, pentylene).

Specific examples of the organic group as R₂₀₁, R₂₀₂ and R₂₀₃ includecorresponding groups in the compounds (ZI-1), (ZI-2) and (ZI-3) whichare described later.

The compound may be a compound having a plurality of structuresrepresented by formula (ZI). For example, the compound may be a compoundhaving a structure where at least one of R₂₀₁ to R₂₀₃ in the compoundrepresented by formula (ZI) is bonded to at least one of R₂₀₁ to R₂₀₃ inanother compound represented by formula (ZI).

The component (ZI) is more preferably a compound (ZI-1), (ZI-2) or(ZI-3) described below.

The compound (ZI-1) is an arylsulfonium compound where at least one ofR₂₀₁ to R₂₀₃ in formula (ZI) is an aryl group, that is, a compoundhaving an arylsulfonium as the cation.

In the arylsulfonium compound, R₂₀₁ to R₂₀₃ all may be an aryl group ora part of R₂₀₁ to R₂₀₃ may be an aryl group with the remaining being analkyl group or a cycloalkyl group.

Examples of the arylsulfonium compound include a triarylsulfoniumcompound, a diarylalkylsulfonium compound, an aryldialkylsulfoniumcompound, a diarylcycloalkylsulfonium compound and anaryldicycloalkylsulfonium compound.

The aryl group in the arylsulfonium compound is preferably an aryl groupsuch as phenyl group and naphthyl group, or a heteroaryl group such asindole residue and pyrrole residue, more preferably a phenyl group or anindole residue. In the case where the arylsulfonium compound has two ormore aryl groups, these two or more aryl groups may be the same ordifferent.

The alkyl group which is present, if desired, in the arylsulfoniumcompound is preferably a linear or branched alkyl group having a carbonnumber of 1 to 15, and examples thereof include a methyl group, an ethylgroup, a propyl group, an n-butyl group, a sec-butyl group and atert-butyl group.

The cycloalkyl group which is present, if desired, in the arylsulfoniumcompound is preferably a cycloalkyl group having a carbon number of 3 to15, and examples thereof include a cyclopropyl group, a cyclobutyl groupand a cyclohexyl group.

The aryl group, alkyl group and cycloalkyl group of R₂₀₁ to R₂₀₃ eachmay have, as the substituent, an alkyl group (for example, an alkylgroup having a carbon number of 1 to 15), a cycloalkyl group (forexample, a cycloalkyl group having a carbon number of 3 to 15), an arylgroup (for example, an aryl group having a carbon number of 6 to 14), analkoxy group (for example, an alkoxy group having a carbon number of 1to 15), a halogen atom, a hydroxyl group or a phenylthio group. Thesubstituent is preferably a linear or branched alkyl group having acarbon number of 1 to 12, a cycloalkyl group having a carbon number of 3to 12, or a linear, branched or cyclic alkoxy group having a carbonnumber of 1 to 12, more preferably an alkyl group having a carbon numberof 1 to 4 or an alkoxy group having a carbon number of 1 to 4. Thesubstituent may be substituted to any one of three members R₂₀₁ to R₂₀₃or may be substituted to all of these three members. In the case whereR₂₀₁ to R₂₀₃ are an aryl group, the substituent is preferablysubstituted at the p-position of the aryl group.

The compound (ZI-2) is described below. The compound (ZI-2) is acompound where each of R₂₀₁ to R₂₀₃ in formula (ZI) independentlyrepresents an aromatic ring-free organic group. The aromatic ring asused herein includes an aromatic ring containing a heteroatom.

The aromatic ring-free organic group as R₂₀₁ to R₂₀₃ generally has acarbon number of 1 to 30, preferably from 1 to 20.

Each of R₂₀₁ to R₂₀₃ is independently preferably an alkyl group, acycloalkyl group, an allyl group or a vinyl group, more preferably alinear, branched or cyclic 2-oxoalkyl group or an alkoxycarbonylmethylgroup, still more preferably a linear or branched 2-oxoalkyl group.

The alkyl group as R₂₀₁ to R₂₀₃ may be either linear or branched andincludes a linear or branched alkyl group preferably having a carbonnumber of 1 to 10 (e.g., methyl, ethyl, propyl, butyl, pentyl). Thealkyl group as R₂₀₁ to R₂₀₃ is preferably a linear or branched2-oxoalkyl group or an alkoxycarbonylmethyl group.

The cycloalkyl group as R₂₀₁ to R₂₀₃ includes a cycloalkyl grouppreferably having a carbon number of 3 to 10 (e.g., cyclopentyl,cyclohexyl, norbornyl). The cycloalkyl group as R₂₀₁ to R₂₀₃ ispreferably a cyclic 2-oxoalkyl group.

The linear, branched or cyclic 2-oxoalkyl group as R₂₀₁ to R₂₀₃ ispreferably a group having >C═O at the 2-position of the above-describedalkyl or cycloalkyl group.

The alkoxy group in the alkoxycarbonylmethyl group as R₂₀₁ to R₂₀₃includes an alkoxy group preferably having a carbon number of 1 to 5(e.g., methoxy, ethoxy, propoxy, butoxy, pentoxy).

R₂₀₁ to R₂₀₃ each may be further substituted by a halogen atom, analkoxy group (for example, an alkoxy group having a carbon number of 1to 5), a hydroxyl group, a cyano group or a nitro group.

The compound (ZI-3) is a compound represented by the following formula(ZI-3), and this is a compound having a phenacylsulfonium saltstructure.

In formula (ZI-3), each of R_(1c) to R_(5c) independently represents ahydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group or ahalogen atom.

Each of R_(6c) and R_(7c) independently represents a hydrogen atom, analkyl group or a cycloalkyl group.

Each of R_(x), and R_(y) independently represents an alkyl group, acycloalkyl group, an allyl group or a vinyl group.

Any two or more members out of R_(1c) to R_(7c), and a pair of R_(x) andR_(y), may combine with each other to form a ring structure,respectively, and the ring structure may contain an oxygen atom, asulfur atom, an ester bond or an amide bond. Examples of the groupformed by combining any two or more members out of R_(1c) to R_(7c) or apair of R_(x), and R_(y) include a butylene group and a pentylene group.

X⁻ represents a non-nucleophilic anion, and examples thereof are thesame as those of the non-nucleophilic anion of X⁻ in formula (ZI).

The alkyl group as R_(1c) to R_(7c) may be linear or branched andincludes, for example, a linear or branched alkyl group having a carbonnumber of 1 to 20, preferably a linear or branched alkyl group having acarbon number of 1 to 12 (such as methyl group, ethyl group, linear orbranched propyl group, linear or branched butyl group and linear orbranched pentyl group).

The cycloalkyl group as R_(1c) to R_(7c) includes a cycloalkyl grouppreferably having a carbon number of 3 to 8 (e.g., cyclopentyl,cyclohexyl).

The alkoxy group as R_(1c) to R_(5c) may be linear, branched or cyclicand includes, for example, an alkoxy group having a carbon number of 1to 10, preferably a linear or branched alkoxy group having a carbonnumber of 1 to 5 (such as methoxy group, ethoxy group, linear orbranched propoxy group, linear or branched butoxy group and linear orbranched pentoxy group), and a cyclic alkoxy group having a carbonnumber of 3 to 8 (e.g., cyclopentyloxy, cyclohexyloxy).

A compound where any one of R_(1c) to R_(5c) is a linear or branchedalkyl group, a cycloalkyl group or a linear, branched or cyclic alkoxygroup is preferred, and a compound where the sum of carbon numbers ofR_(1c) to R_(5c) is from 2 to 15 is more preferred. Thanks to thisconstruction, the solubility in a solvent is more enhanced andgeneration of particles during storage is suppressed.

The alkyl group as R_(x) and R_(y) is the same as the alkyl group ofR_(1c) to R_(7c). The alkyl group as R_(x) and R_(y) is preferably alinear or branched 2-oxoalkyl group or an alkoxycarbonylmethyl group.

The cycloalkyl group as R_(x), and R_(y) is the same as the cycloalkylgroup of R_(1c) to R_(7c). The cycloalkyl group as R_(x) and R_(y) ispreferably a cyclic 2-oxoalkyl group.

The linear, branched or cyclic 2-oxoalkyl group includes a grouphaving >C═O at the 2-position of the alkyl group or cycloalkyl group ofR_(1c) to R_(7c).

The alkoxy group in the alkoxycarbonylmethyl group is the same as thealkoxy group of R_(1c) to R_(5c).

R_(x) and R_(y) each is preferably an alkyl group having a carbon numberof 4 or more, more preferably 6 or more, still more preferably 8 ormore.

In formulae (ZII) and (ZIII), each of R₂₀₄ to R₂₀₇ independentlyrepresents an aryl group, an alkyl group or a cycloalkyl group.

The aryl group of R₂₀₄ to R₂₀₇ is preferably a phenyl group or anaphthyl group, more preferably a phenyl group.

The alkyl group as R₂₀₄ to R₂₀₇ may be linear or branched and includes alinear or branched alkyl group preferably having a carbon number of 1 to10 (e.g., methyl, ethyl, propyl, butyl, pentyl).

The cycloalkyl group as R₂₀₄ to R₂₀₇ includes a cycloalkyl grouppreferably having a carbon number of 3 to 10 (e.g., cyclopentyl,cyclohexyl, norbornyl).

R₂₀₄ to R₂₀₇ each may have a substituent. Examples of the substituentwhich R₂₀₄ to R₂₀₇ each may have include an alkyl group (for example, analkyl group having a carbon number of 1 to 15), a cycloalkyl group (forexample, a cycloalkyl group having a carbon number of 3 to 15), an arylgroup (for example, an aryl group having a carbon number of 6 to 15), analkoxy group (for example, an alkoxy group having a carbon number of 1to 15), a halogen atom, a hydroxyl group and a phenylthio group.

X⁻ represents a non-nucleophilic anion and is the same as thenon-nucleophilic anion of X⁻ in formula (ZI).

Out of the compounds capable of generating an acid upon irradiation withan actinic ray or radiation, preferred compounds further include thecompounds represented by the following formulae (ZIV), (ZV) and (ZVI):

In formulae (ZIV) to (ZVI), each of Ar₃ and Ar₄ independently representsan aryl group.

R₂₀₈ represents an alkyl group or an aryl group.

Each of R₂₀₉ and R₂₁₀ independently represents an alkyl group, an arylgroup or an electron-withdrawing group.

R₂₀₈ is preferably an aryl group.

R₂₀₉ is preferably an electron-withdrawing group, more preferably acyano group or a fluoroalkyl group.

A represents an alkylene group, an alkenylene group or an arylene group.

The compound capable of generating an acid upon irradiation with anactinic ray or radiation is preferably a compound represented by any oneof formulae (ZI) to (ZIII).

The compound (B) is preferably a compound capable of generating afluorine atom-containing aliphatic sulfonic acid or a fluorineatom-containing benzenesulfonic acid upon irradiation with an actinicray or radiation.

The compound (B) preferably has a triphenylsulfonium structure.

The compound (B) is preferably a triphenylsulfonium salt compound havinga fluorine-unsubstituted alkyl or cycloalkyl group in the cation moiety.

Particularly preferred examples out of the compounds capable ofgenerating an acid upon irradiation with an actinic ray or radiation areset forth below.

One of these photo-acid generators may be used alone, or two or morekinds thereof may be used in combination. In the case of using two ormore kinds of photo-acid generators in combination, compounds capable ofgenerating two kinds of organic acids differing in the total atom numberexcept for hydrogen atom by 2 or more are preferably combined.

The content of the photo-acid generator is preferably from 0.1 to 20mass %, more preferably from 0.5 to 10 mass %, still more preferablyfrom 1 to 7 mass %, based on the entire solid content of the resistcomposition.

(C) Solvent

Examples of the solvent which can be used for dissolving respectivecomponents described above to prepare a positive tone resist compositioninclude an organic solvent such as alkylene glycol monoalkyl ethercarboxylate, alkylene glycol monoalkyl ether, alkyl lactate, alkylalkoxypropionate, cyclic lactone having a carbon number of 4 to 10,monoketone compound having a carbon number of 4 to 10 which may containa ring, alkylene carbonate, alkyl alkoxyacetate and alkyl pyruvate.

Preferred examples of the alkylene glycol monoalkyl ether carboxylateinclude propylene glycol monomethyl ether acetate, propylene glycolmonoethyl ether acetate, propylene glycol monopropyl ether acetate,propylene glycol monobutyl ether acetate, propylene glycol monomethylether propionate, propylene glycol monoethyl ether propionate, ethyleneglycol monomethyl ether acetate and ethylene glycol monoethyl etheracetate.

Preferred examples of the alkylene glycol monoalkyl ether includepropylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol monopropyl ether, propylene glycol monobutyl ether,ethylene glycol monomethyl ether and ethylene glycol monoethyl ether.

Preferred examples of the alkyl lactate include methyl lactate, ethyllactate, propyl lactate and butyl lactate.

Preferred examples of the alkyl alkoxypropionate include ethyl3-ethoxypropionate, methyl 3-methoxypropionate, methyl3-ethoxypropionate and ethyl 3-methoxypropionate.

Preferred examples of the cyclic lactone having a carbon number of 4 to10 include β-propiolactone, α-butyrolactone, γ-butyrolactone,α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone,γ-caprolactone, γ-octanoic lactone and α-hydroxy-γ-butyrolactone.

Preferred examples of the monoketone compound having a carbon number of4 to 10 which may contain a ring include 2-butanone, 3-methylbutanone,pinacolone, 2-pentanone, 3-pentanone, 3-methyl-2-pentanone,4-methyl-2-pentanone, 2-methyl-3-pentanone, 4,4-dimethyl-2-pentanone,2,4-dimethyl-3-pentanone, 2,2,4,4-tetramethyl-3-pentanone, 2-hexanone,3-hexanone, 5-methyl-3-hexanone, 2-heptanone, 3-heptanone, 4-heptanone,2-methyl-3-heptanone, 5-methyl-3-heptanone, 2,6-dimethyl-4-heptanone,2-octanone, 3-octanone, 2-nonanone, 3-nonanone, 5-nonanone, 2-decanone,3-decanone, 4-decanone, 5-hexen-2-one, 3-penten-2-one, cyclopentanone,2-methylcyclopentanone, 3-methylcyclopentanone,2,2-dimethylcyclopentanone, 2,4,4-trimethylcyclopentanone,cyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone,4-ethylcyclohexanone, 2,2-dimethylcyclohexanone,2,6-dimethylcyclohexanone, 2,2,6-trimethylcyclohexanone, cycloheptanone,2-methylcycloheptanone and 3-methylcycloheptanone.

Preferred examples of the alkylene carbonate include propylenecarbonate, vinylene carbonate, ethylene carbonate and butylenecarbonate.

Preferred examples of the alkyl alkoxyacetate include 2-methoxyethylacetate, 2-ethoxyethyl acetate, 2-(2-ethoxyethoxy)ethyl acetate,3-methoxy-3-methylbutyl acetate and 1-methoxy-2-propyl acetate.

Preferred examples of the alkyl pyruvate include methyl pyruvate, ethylpyruvate and propyl pyruvate.

The solvent which can be preferably used is a solvent having a boilingpoint of 130° C. or more at ordinary temperature under atmosphericpressure, and specific examples thereof include cyclopentanone,γ-butyrolactone, cyclohexanone, ethyl lactate, ethylene glycol monoethylether acetate, propylene glycol monomethyl ether acetate, ethyl3-ethoxypropionate, ethyl pyruvate, 2-ethoxyethyl acetate,2-(2-ethoxyethoxy)ethyl acetate and propylene carbonate.

In the present invention, one of these solvents may be used alone, ortwo or more kinds thereof may be used in combination.

In the present invention, a mixed solvent prepared by mixing a solventcontaining a hydroxyl group in the structure and a solvent notcontaining a hydroxyl group may be used as the organic solvent.

Examples of the solvent containing a hydroxyl group include ethyleneglycol, ethylene glycol monomethyl ether, ethylene glycol monoethylether, propylene glycol, propylene glycol monomethyl ether, propyleneglycol monoethyl ether and ethyl lactate. Among these, propylene glycolmonomethyl ether and ethyl lactate are preferred.

Examples of the solvent not containing a hydroxyl group includepropylene glycol monomethyl ether acetate, ethyl ethoxypropionate,2-heptanone, γ-butyrolactone, cyclohexanone, butyl acetate,N-methylpyrrolidone, N,N-dimethylacetamide and dimethylsulfoxide. Amongthese, propylene glycol monomethyl ether acetate, ethylethoxypropionate, 2-heptanone, γ-butyrolactone, cyclohexanone and butylacetate are preferred, and propylene glycol monomethyl ether acetate,ethyl ethoxypropionate and 2-heptanone are most preferred.

The mixing ratio (by mass) between the solvent containing a hydroxylgroup and the solvent not containing a hydroxyl group is from 1/99 to99/1, preferably from 10/90 to 90/10, more preferably from 20/80 to60/40. A mixed solvent in which the solvent not containing a hydroxylgroup is contained in an amount of 50 mass % or more is preferred inview of coating uniformity.

The solvent is preferably a mixed solvent of two or more kinds ofsolvents including propylene glycol monomethyl ether acetate.

The entire solid content concentration in the resist composition isgenerally from 1 to 10 mass %, preferably from 1 to 8.0 mass %, morepreferably from 1.0 to 6.0 mass %.

(D) Resin Having at Least Either a Fluorine Atom or a Silicon Atom

The resist composition of the present invention preferably contains (D)a resin having at least either a fluorine atom or a silicon atom.

In the resin (D), the fluorine atom or silicon atom may be present inthe main chain of the resin or may be substituted to the side chain.

The resin (D) is preferably a resin having a fluorine atom-containingalkyl group, a fluorine atom-containing cycloalkyl group or a fluorineatom-containing aryl group, as a fluorine atom-containing partialstructure.

The fluorine atom-containing alkyl group (preferably having a carbonnumber of 1 to 10, more preferably from 1 to 4) is a linear or branchedalkyl group with at least one hydrogen atom being substituted by afluorine atom and may further have another substituent.

The fluorine atom-containing cycloalkyl group is a monocyclic orpolycyclic cycloalkyl group with at least one hydrogen atom beingsubstituted by a fluorine atom and may further have another substituent.

The fluorine atom-containing aryl group is an aryl group (e.g., phenyl,naphthyl) with at least one hydrogen atom being substituted by afluorine atom and may further have another substituent.

Specific examples of the fluorine atom-containing alkyl group, fluorineatom-containing cycloalkyl group and fluorine atom-containing aryl groupare set forth below, but the present invention is not limited thereto.

In formulae (f1) to (f3), each of R₅₇ to R₆₈ independently represents ahydrogen atom, a fluorine atom or an alkyl group, provided that at leastone of R₅₇ to R₆₁, at least one of R₆₂ to R₆₄ and at least one of R₆₅ toR₆₈ are a fluorine atom or an alkyl group (preferably having a carbonnumber of 1 to 4) with at least one hydrogen atom being substituted by afluorine atom. It is preferred that R₅₇ to R₆₁ and R₆₅ to R₆₇ all are afluorine atom. Each of R₆₂, R₆₃ and R₆₈ is preferably an alkyl group(preferably having a carbon number of 1 to 4) with at least one hydrogenatom being substituted by a fluorine atom, more preferably aperfluoroalkyl group having a carbon number of 1 to 4. R₆₂ and R₆₃ maycombine with each other to form a ring.

Specific examples of the group represented by formula (f1) includep-fluorophenyl group, pentafluorophenyl group and3,5-di(trifluoromethyl)phenyl group.

Specific examples of the group represented by formula (f2) includetrifluoroethyl group, pentafluoropropyl group, pentafluoroethyl group,heptafluorobutyl group, hexafluoroisopropyl group, heptafluoroisopropylgroup, hexafluoro(2-methyl)isopropyl group, nonafluorobutyl group,octafluoroisobutyl group, nonafluorohexyl group, nonafluoro-tert-butylgroup, perfluoroisopentyl group, perfluorooctyl group,perfluoro(trimethyl)hexyl group, 2,2,3,3-tetrafluorocyclobutyl group andperfluorocyclohexyl group. Among these, hexafluoroisopropyl group,heptafluoroisopropyl group, hexafluoro(2-methyl)isopropyl group,octafluoroisobutyl group, nonafluoro-tert-butyl group andperfluoroisopentyl group are preferred, and hexafluoroisopropyl groupand heptafluoroisopropyl group are more preferred.

Specific examples of the group represented by formula (f3) include—C(CF₃)₂OH, —C(C₂F₅)₂OH, —C(CF₃)(CH₃)OH and —CH(CF₃)OH, with —C(CF₃)₂OHbeing preferred.

The resin (D) is preferably a resin having an alkylsilyl structure(preferably a trialkylsilyl group) or a cyclic siloxane structure, as asilicon atom-containing partial structure.

Specific examples of the alkylsilyl structure and cyclic siloxanestructure include the groups represented by the following formulae(CS-1) to (CS-3):

In formulae (CS-1) to (CS-3), each of R₁₂ to R₂₆ independentlyrepresents a linear or branched alkyl group (preferably having a carbonnumber of 1 to 20) or a cycloalkyl group (preferably having a carbonnumber of 3 to 20).

Each of L₃ to L₅ represents a single bond or a divalent linking group.The divalent linking group is a sole group or a combination of two ormore groups selected from the group consisting of an alkylene group, aphenylene group, an ether group, a thioether group, a carbonyl group, anester group, an amide group, a urethane group and a ureylene group.

n represents an integer of 1 to 5.

The resin (D) includes a resin containing at least one member selectedfrom the group consisting of repeating units represented by thefollowing formulae (C-I) to (C-V):

In formulae (C-I) to (C-V), each of R₁ to R₃ independently represents ahydrogen atom, a fluorine atom, a linear or branched alkyl group havinga carbon number of 1 to 4, or a linear or branched fluorinated alkylgroup having a carbon number of 1 to 4.

Each of W₁ and W₂ represents an organic group having at least either afluorine atom or a silicon atom.

Each R₄ to R₇ independently represents a hydrogen atom, a fluorine atom,a linear or branched alkyl group having a carbon number of 1 to 4, or alinear or branched fluorinated alkyl group having a carbon number of 1to 4, provided that at least one of R₄ to R₇ represents a fluorine atom.R₄ and R₅, or R₆ and R₇ may form a ring.

R₈ represents a hydrogen atom or a linear or branched alkyl group havinga carbon number of 1 to 4.

R₉ represents a linear or branched alkyl group having a carbon number of1 to 4, or a linear or branched fluorinated alkyl group having a carbonnumber of 1 to 4.

Each of L₁ and L₂ represents a single bond or a divalent linking groupand is the same as L₃ to L₅ above.

Q represents a monocyclic or polycyclic aliphatic group, that is, anatomic group for forming an alicyclic structure, including the twobonded carbon atoms (C—C).

Each of R₃₀ and R₃₁ independently represents a hydrogen or fluorineatom.

Each of R₃₂ and R₃₃ independently represents an alkyl group, acycloalkyl group, a fluorinated alkyl group or a fluorinated cycloalkylgroup.

Here, the repeating unit represented by formula (C-V) has at least onefluorine atom in at least one member out of R₃₀, R₃₁, R₃₂ and R₃₃.

The resin (D) preferably has a repeating unit represented by formula(C-I), more preferably a repeating unit represented by any one of thefollowing formulae (C-Ia) to (C-Id):

In formulae (C-Ia) to (C-Id), each of R₁₀ and R₁₁ represents a hydrogenatom, a fluorine atom, a linear or branched alkyl group having a carbonnumber of 1 to 4, or a linear or branched fluorinated alkyl group havinga carbon number of 1 to 4.

Each of W₃ to W₆ represents an organic group having one or more atoms ofat least either a fluorine atom or a silicon atom.

When W₁ to W₆ are an organic group having a fluorine atom, the organicgroup is preferably a fluorinated linear or branched alkyl group orcycloalkyl group having a carbon number of 1 to 20, or a fluorinatedlinear, branched or cyclic alkyl ether group having a carbon number of 1to 20.

Examples of the fluorinated alkyl group of W₁ to W₆ include atrifluoroethyl group, a pentafluoropropyl group, a hexafluoroisopropylgroup, a hexafluoro(2-methyl)isopropyl group, a heptafluorobutyl group,a heptafluoroisopropyl group, an octafluoroisobutyl group, anonafluorohexyl group, a nonafluoro-tert-butyl group, aperfluoroisopentyl group, a perfluorooctyl group and aperfluoro(trimethyl)hexyl group.

When W₁ to W₆ are an organic group having a silicon atom, the organicgroup preferably has an alkylsilyl structure or a cyclic siloxanestructure. Specific examples thereof include the groups represented byformulae (CS-1) to (CS-3).

Specific examples of the repeating unit represented by formula (C-I) areset forth below. X represents a hydrogen atom, —CH₃, —F or —CF₃.

The resin (D) is preferably any one resin selected from the following(D-1) to (D-6):

(D-1) a resin containing (a) a repeating unit having a fluoroalkyl group(preferably having a carbon number of 1 to 4), more preferably a resincontaining only the repeating unit (a),

(D-2) a resin containing (b) a repeating unit having a trialkylsilylgroup or a cyclic siloxane structure, more preferably a resin containingonly the repeating unit (b),

(D-3) a resin containing (a) a repeating unit having a fluoroalkyl group(preferably having a carbon number of 1 to 4) and (c) a repeating unithaving a branched alkyl group (preferably having a carbon number of 4 to20), a cycloalkyl group (preferably having a carbon number of 4 to 20),a branched alkenyl group (preferably having a carbon number of 4 to 20),a cycloalkenyl group (preferably having a carbon number of 4 to 20) oran aryl group (preferably having a carbon number of 6 to 20), morepreferably a copolymerization resin of the repeating unit (a) and therepeating unit (c),

(D-4) a resin containing (b) a repeating unit having a trialkylsilylgroup or a cyclic siloxane structure and (c) a repeating unit having abranched alkyl group (preferably having a carbon number of 4 to 20), acycloalkyl group (preferably having a carbon number of 4 to 20), abranched alkenyl group (preferably having a carbon number of 4 to 20), acycloalkenyl group (preferably having a carbon number of 4 to 20) or anaryl group (preferably having a carbon number of 6 to 20), morepreferably a copolymerization resin of the repeating unit (b) and therepeating unit (c),

(D-5) a resin containing (a) a repeating unit having a fluoroalkyl group(preferably having a carbon number of 1 to 4) and (b) a repeating unithaving a trialkylsilyl group or a cyclic siloxane structure, morepreferably a copolymerization resin of the repeating unit (a) and therepeating unit (b), and

(D-6) a resin containing (a) a repeating unit having a fluoroalkyl group(preferably having a carbon number of 1 to 4), (b) a repeating unithaving a trialkylsilyl group or a cyclic siloxane structure, and (c) arepeating unit having a branched alkyl group (preferably having a carbonnumber of 4 to 20), a cycloalkyl group (preferably having a carbonnumber of 4 to 20), a branched alkenyl group (preferably having a carbonnumber of 4 to 20), a cycloalkenyl group (preferably having a carbonnumber of 4 to 20) or an aryl group (preferably having a carbon numberof 6 to 20), more preferably a copolymerization resin of the repeatingunit (a), the repeating unit (b) and the repeating unit (c).

As for the repeating unit (c) having a branched alkyl group, acycloalkyl group, a branched alkenyl group, a cycloalkenyl group or anaryl group in the resins (D-3), (D-4) and (D-6), an appropriatefunctional group can be introduced considering thehydrophilicity/hydrophobicity, interaction and the like, but in view offollowability of immersion liquid or receding contact angle, afunctional group having no polar group is preferred.

In the resins (D-3), (D-4) and (D-6), the content of the repeating unit(a) having a fluoroalkyl group and/or the repeating unit (b) having atrialkylsilyl group or a cyclic siloxane structure is preferably from 20to 99 mol %.

The resin (D) is preferably a resin having a repeating unit representedby the following formula (Ia):

In formula (Ia), Rf represents a fluorine atom or an alkyl group with atleast one hydrogen atom being substituted by a fluorine atom.

R₁ represents an alkyl group.

R₂ represents a hydrogen atom or an alkyl group.

In formula (Ia), the alkyl group with at least one hydrogen atom beingsubstituted by a fluorine atom of Rf is preferably an alkyl group havinga carbon number of 1 to 3, more preferably a trifluoromethyl group.

The alkyl group of R₁ is preferably a linear or branched alkyl grouphaving a carbon number of 3 to 10, more preferably a branched alkylgroup having a carbon number of 3 to 10.

R₂ is preferably a linear or branched alkyl group having a carbon numberof 1 to 10, more preferably a linear or branched alkyl group having acarbon number of 3 to 10.

Specific examples of the repeating unit represented by formula (Ia) areset forth below, but the present invention is not limited thereto.

X═F or CF₃

The repeating unit represented by formula (Ia) can be formed bypolymerizing a compound represented by the following formula (I):

In formula (I), Rf represents a fluorine atom or an alkyl group with atleast one hydrogen atom being substituted by a fluorine atom.

R₁ represents an alkyl group.

R₂ represents a hydrogen atom or an alkyl group.

Rf, R₁ and R₂ in formula (I) have the same meanings as Rf, R₁ and R₂ informula (Ia).

As for the compound represented by formula (I), a commercially availableproduct or a compound synthesized may be used. In the case ofsynthesizing the compound, this can be attained by converting a2-trifluoromethyl methacrylic acid into an acid chloride and thenesterifying the acid chloride.

The resin (D) containing a repeating unit represented by formula (Ia)preferably further contains a repeating unit represented by thefollowing formula (III):

In formula (III), R₄ represents an alkyl group, a cycloalkyl group, analkenyl group, a cycloalkenyl group, a trialkylsilyl group or a grouphaving a cyclic siloxane structure.

L₆ represents a single bond or a divalent linking group.

R represents a hydrogen atom or an alkyl group (which may be substitutedby a fluorine atom, etc.). The alkyl group represented by R preferablyhas a carbon number of 1 to 4. R is preferably a hydrogen atom, a methylgroup or a trifluoromethyl group, and a hydrogen atom and a methyl groupare particularly preferred. In formula (III), the alkyl group of R₄ ispreferably a linear or branched alkyl group having a carbon number of 3to 20.

The cycloalkyl group is preferably a cycloalkyl group having a carbonnumber of 3 to 20.

The alkenyl group is preferably an alkenyl group having a carbon numberof 3 to 20.

The cycloalkenyl group is preferably a cycloalkenyl group having acarbon number of 3 to 20.

The trialkylsilyl group is preferably a trialkylsilyl group having acarbon number of 3 to 20.

The group having a cyclic siloxane structure is preferably a groupcontaining a cyclic siloxane structure having a carbon number of 3 to20.

The divalent linking group of L₆ is preferably an alkylene group(preferably having a carbon number of 1 to 5) or an oxy group.

Specific examples of the resin (D) having a repeating unit representedby formula (Ia) are set forth below, but the present invention is notlimited thereto.

The resin (D) is preferably a resin containing a repeating unitrepresented by the following formula (II) and a repeating unitrepresented by the following formula (III):

In formulae (II) and (III), Rf represents a fluorine atom or an alkylgroup with at least one hydrogen atom being substituted by a fluorineatom.

R₃ represents an alkyl group, a cycloalkyl group, an alkenyl group, acycloalkenyl group, or a group formed by combining two or more membersthereof.

R₄ represents an alkyl group, a cycloalkyl group, an alkenyl group, acycloalkenyl group, a trialkylsilyl group, a group having a cyclicsiloxane structure, or a group formed by combining two or more membersthereof.

In the alkyl group, cycloalkyl group, alkenyl group, cycloalkenyl groupand trialkylsilyl group of R₃ and R₄, a functional group can beintroduced but in view of followability of immersion liquid, afunctional group having no polar group is preferred, and anunsubstituted functional group is more preferred.

R represents a hydrogen atom or an alkyl group (which may be substitutedby a fluorine atom, etc.). The alkyl group represented by R preferablyhas a carbon number of 1 to 4. R is preferably a hydrogen atom, a methylgroup or a trifluoromethyl group, and a hydrogen atom and a methyl groupare particularly preferred.

L₆ represents a single bond or a divalent linking group.

0<m<100.

0<n<100.

In formula (II), Rf has the same meaning as Rf in formula (Ia).

The alkyl group of R₃ is preferably a linear or branched alkyl grouphaving a carbon number of 3 to 20.

The cycloalkyl group is preferably a cycloalkyl group having a carbonnumber of 3 to 20.

The alkenyl group is preferably an alkenyl group having a carbon numberof 3 to 20.

The cycloalkenyl group is preferably a cycloalkenyl group having acarbon number of 3 to 20.

L₆ is preferably a single bond, a methylene group, an ethylene group oran ether group.

m and n are preferably from 30 to 70 and from 30 to 70, respectively,more preferably from 40 to 60 and from 40 to 60, respectively.

Specific examples of the resin (D) containing a repeating unitrepresented by formula (II) and a repeating unit represented by formula(III) are set forth below, but the present invention is not limitedthereto.

The resin (D) may contain a repeating unit represented by the followingformula (VIII):

In formula (VIII), Z₂ represents —O— or —N(R₄₁)—. R₄₁ represents ahydrogen atom, an alkyl group or —OSO₂—R₄₂. R₄₂ represents an alkylgroup, a cycloalkyl group or a camphor residue. The alkyl group of R₄₁and R₄₂ may be substituted by a halogen atom (preferably fluorine atom)or the like.

The resin (D) is preferably solid at ordinary temperature (25° C.).Furthermore, the glass transition temperature (Tg) is preferably from 50to 200° C., more preferably from 80 to 160° C.

When the resin is solid at 25° C., this means that the melting point is25° C. or more.

The glass transition temperature (Tg) can be measured by a scanningcalorimeter (Differential Scanning Calorimeter). For example, the glasstransition temperature can be measured by once heating and then coolingthe sample, again raising the temperature at 5° C./min, and analyzingthe value when the specific volume is changed.

The resin (D) is preferably stable to an acid and insoluble in an alkalideveloper.

In view of followability of immersion liquid, the resin (D) preferablycontains none of (x) an alkali-soluble group, (y) a group capable ofdecomposing by the action of an alkali (alkali developer) to increasethe solubility in an alkali developer, and (z) a group capable ofdecomposing by the action of an acid to increase the solubility in adeveloper.

In the resin (D), the total amount of repeating units having analkali-soluble group or a group whose solubility in a developerincreases by the action of an acid or alkali is preferably 20 mol % orless, more preferably from 0 to 10 mol %, still more preferably from 0to 5 mol %, based on all repeating units constituting the resin (D).

Also, unlike a surfactant generally used for resists, the resin (D) doesnot have an ionic bond or a hydrophilic group such as(poly(oxyalkylene)) group. If the resin (D) contains a hydrophilic polargroup, the followability of immersion water tends to decrease.Therefore, it is more preferred not to contain a polar group selectedfrom a hydroxyl group, alkylene glycols and a sulfone group.Furthermore, an ether group bonded to the carbon atom of the main chainthrough a linking group is preferably not contained because thehydrophilicity increases and the followability of immersion liquiddeteriorates. On the other hand, an ether group bonded directly to thecarbon atom of the main chain as in formula (III) can sometimes expressactivity as a hydrophobic group and is preferred.

Examples of the alkali-soluble group (x) include groups having aphenolic hydroxyl group, a carboxylic acid group, a fluorinated alcoholgroup, a sulfonic acid group, a sulfonamide group, a sulfonylimidegroup, an (alkylsulfonyl)(alkylcarbonyl)methylene group, an(alkylsulfonyl)(alkylcarbonyl)imide group, a bis(alkylcarbonyl)methylenegroup, a bis(alkylcarbonyl)imide group, a bis(alkylsulfonyl)methylenegroup, a bis(alkylsulfonyl)imide group, a tris(alkylcarbonyl)methylenegroup or a tris(alkylsulfonyl)methylene group.

Examples of the group (y) capable of decomposing by the action of analkali (alkali developer) to increase the solubility in an alkalideveloper include a lactone group, an ester group, a sulfonamide group,an acid anhydride and an acid imide group.

Examples of the group (z) capable of decomposing by the action of anacid to increase the solubility in a developer include the same groupsas those of the acid-decomposable group in the acid-decomposable resin(A).

However, the repeating unit represented by the following formula (pA-c)is not or scarcely decomposed by the action of an acid as compared withthe acid-decomposable group of the resin (A) and is regarded assubstantially non-acid-decomposable.

In formula (pA-c), Rp₂ represents a hydrocarbon group having a tertiarycarbon atom bonded to the oxygen atom in the formula.

In the case where the resin (D) contains a silicon atom, the siliconatom content is preferably from 2 to 50 mass %, more preferably from 2to 30 mass %, based on the molecular weight of the resin (D). Also, thesilicon atom-containing repeating unit preferably occupies from 10 to100 mass %, more preferably from 20 to 100 mass %, in the resin (D).

In the case where the resin (D) contains a fluorine atom, the fluorineatom content is preferably from 5 to 80 mass %, more preferably from 10to 80 mass %, based on the molecular weight of the resin (D). Also, thefluorine atom-containing repeating unit preferably occupies from 10 to100 mass %, more preferably from 30 to 100 mass %, in the resin (D).

The standard polystyrene-reduced weight average molecular of the resin(D) is preferably from 1,000 to 100,000, more preferably from 1,000 to50,000, still more preferably from 2,000 to 15,000, yet still morepreferably from 3,000 to 15,000.

The residual monomer amount in the resin (D) is preferably from 0 to 10mass %, more preferably from 0 to 5 mass %, still more preferably from 0to 1 mass %. Also, in view of the resolution, resist profile, and sidewall, roughness or the like of the resist pattern, the molecular weightdistribution (Mw/Mn, also called dispersity) is preferably from 1 to 5,more preferably from 1 to 3, still more preferably from 1 to 1.5.

The amount added of the resin (D) in the resist composition ispreferably from 0.1 to 20 mass %, more preferably from 0.1 to 10 mass %,still more preferably from 0.1 to 5 mass %, even still more preferablyfrom 0.2 to 3.0 mass %, yet even still more preferably from 0.3 to 2.0mass %, based on the entire solid content of the resist composition.

In the resin (D), similarly to the acid-decomposable resin (A),impurities such as metal are of course little contained and as well, thecontent of residual monomers or oligomer components is preferably notmore than a specific value, for example, 0.1 mass % by HPLC. Bysatisfying these conditions, not only the resist can be improved in thesensitivity, resolution, process stability, pattern profile and the likebut also a resist free from extraneous substances in liquid or changewith aging in the sensitivity and the like can be obtained.

As for the resin (D), various commercially available products may beused or the resin may be synthesize by an ordinary method (for example,radical polymerization)). Examples of the synthesis method in generalinclude a batch polymerization method of dissolving monomer species andan initiator in a solvent and heating the solution, thereby effectingthe polymerization, and a dropping polymerization method of addingdropwise a solution containing monomer species and an initiator to aheated solvent over 1 to 10 hours. A dropping polymerization method ispreferred. Examples of the reaction solvent include tetrahydrofuran,1,4-dioxane, ethers such as diisopropyl ether, ketones such as methylethyl ketone and methyl isobutyl ketone, an ester solvent such as ethylacetate, an amide solvent such as dimethylformamide anddimethylacetamide, and the later-described solvent capable of dissolvingthe composition of the present invention, such as propylene glycolmonomethyl ether acetate, propylene glycol monomethyl ether andcyclohexanone. The polymerization is more preferably performed using thesame solvent as the solvent used in the resist composition of thepresent invention. By the use of this solvent, generation of particlesduring storage can be suppressed.

The polymerization reaction is preferably performed in an inert gasatmosphere such as nitrogen and argon. As for the polymerizationinitiator, the polymerization is started using a commercially availableradical initiator (e.g., azo-based initiator, peroxide). The radicalinitiator is preferably an azo-based initiator, and an azo-basedinitiator having an ester group, a cyano group or a carboxyl group ispreferred. Preferred examples of the initiator includeazobisisobutyronitrile, azobisdimethylvaleronitrile and dimethyl2,2′-azobis(2-methylpropionate). A chain transfer agent may also beused, if desired. The reaction concentration is usually from 5 to 50mass %, preferably from 20 to 50 mass %, more preferably from 30 to 50mass %, and the reaction temperature is usually from 10 to 150° C.,preferably from 30 to 120° C., more preferably from 60 to 100° C.

After the completion of reaction, the reaction product is allowed tocool to room temperature and purified. The purification may be performedby a normal method, for example, a liquid-liquid extraction method ofcombining water washing with an appropriate solvent to remove residualmonomers or oligomer components; a purification method in a solutionsate, such as ultrafiltration of extracting and removing only polymershaving a molecular weight lower than a specific molecular weight; areprecipitation method of adding dropwise the resin solution in a poorsolvent to solidify the resin in the poor solvent and thereby removeresidual monomers and the like; or a purification method in a solidstate, such as washing of the resin slurry with a poor solvent afterseparation by filtration. For example, the resin is precipitated as asolid through contact with a solvent in which the resin is sparinglysoluble or insoluble (poor solvent) and which is in a volume amount of10 times or less, preferably from 10 to 5 times, the reaction solution.

The solvent used at the operation of precipitation or reprecipitationfrom the polymer solution (precipitation or reprecipitation solvent) maybe sufficient if it is a poor solvent for the polymer, and the solventused may be appropriately selected according to the kind of the polymerfrom, for example, a hydrocarbon (an aliphatic hydrocarbon such aspentane, hexane, heptane and octane; an alicyclic hydrocarbon such ascyclohexane and methylcyclohexane; and an aromatic hydrocarbon such asbenzene, toluene and xylene), a halogenated hydrocarbon (a halogenatedaliphatic hydrocarbon such as methylene chloride, chloroform and carbontetrachloride; and a halogenated aromatic hydrocarbon such aschlorobenzene and dichlorobenzene), a nitro compound (e.g.,nitromethane, nitroethane), a nitrile (e.g., acetonitrile,benzonitrile), an ether (a chain ether such as diethyl ether,diisopropyl ether and dimethoxyethane; and a cyclic ether such astetrahydrofuran and dioxane), a ketone (e.g., acetone, methyl ethylketone, diisobutyl ketone), an ester (e.g., ethyl acetate, butylacetate), a carbonate (e.g., dimethyl carbonate, diethyl carbonate,ethylene carbonate, propylene carbonate), an alcohol (e.g., methanol,ethanol, propanol, isopropyl alcohol, butanol), a carboxylic acid (e.g.,acetic acid), water, and a mixed solvent containing such a solvent.

Among these, the precipitation or reprecipitation solvent is preferablya solvent containing at least an alcohol (particularly methanol or thelike) or water. In such a solvent containing at least a hydrocarbon, theratio of the alcohol (particularly methanol or the like) to othersolvents (for example, an ester such as ethyl acetate, and ethers suchas tetrahydrofuran) is approximately, for example, the former/the latter(volume ratio, at 25° C.)=from 10/90 to 99/1, preferably the former/thelatter (volume ratio, at 25° C.)=from 30/70 to 98/2, more preferably theformer/the latter (volume ratio, at 25° C.)=from 50/50 to 97/3.

The amount of the precipitation or reprecipitation solvent used may beappropriately selected by taking into account the efficiency, yield andthe like, but in general, the amount used is from 100 to 10,000 parts bymass, preferably from 200 to 2,000 parts by mass, more preferably from300 to 1,000 parts by mass, per 100 parts by mass of the polymersolution.

The nozzle bore diameter at the time of feeding the polymer solutioninto a precipitation or reprecipitation solvent (poor solvent) ispreferably 4 mmφ or less (for example, from 0.2 to 4 mmφ), and thefeeding rate (dropping rate) of the polymer solution into the poorsolvent is, for example, in terms of the linear velocity, from 0.1 to 10m/sec, preferably on the order of 0.3 to 5 m/sec.

The precipitation or reprecipitation operation is preferably performedunder stirring. Examples of the stirring blade which can be used forstirring include a disc turbine, a fan turbine (including paddle), acurved vane turbine, a feathering turbine, a Pfaudler type, a bullmargin type, an angled vane fan turbine, a propeller, a multistage type,an anchor type (or horseshoe type), a gate type, a double ribbon and ascrew. The stirring is preferably further performed for 10 minutes ormore, more preferably 20 minutes or more, after the completion offeeding of the polymer solution. If the stirring time is short, themonomer content in the polymer particle may not be sufficiently reduced.The mixing and stirring of the polymer solution and the poor solvent mayalso be performed using a line mixer instead of the stirring blade.

The temperature at the precipitation or reprecipitation may beappropriately selected by taking into account the efficiency oroperability, but the temperature is usually on the order of 0 to 50° C.,preferably in the vicinity of room temperature (for example,approximately from 20 to 35° C.). The precipitation or reprecipitationoperation may be performed using a commonly employed mixing vessel suchas stirring tank according to a known method such as batch system andcontinuous system.

The precipitated or reprecipitated particulate polymer is usuallysubjected to commonly employed solid-liquid separation such asfiltration and centrifugation, then dried and used. The filtration isperformed using a solvent-resistant filter element preferably underpressure. The drying is performed under atmospheric pressure or reducedpressure (preferably under reduced pressure) at a temperature ofapproximately from 30 to 100° C., preferably on the order of 30 to 50°C.

Incidentally, after the resin is once precipitated and separated, theresin may be again dissolved in a solvent and then put into contact witha solvent in which the resin is sparingly soluble or insoluble.

More specifically, there may be used a method comprising, after thecompletion of radical polymerization reaction, precipitating a resin bybringing the polymer into contact with a solvent in which the polymer issparingly soluble or insoluble (step a), separating the resin from thesolution (step b), anew dissolving the resin in a solvent to prepare aresin solution A (step c), precipitating a resin solid by bringing theresin solution A into contact with a solvent in which the resin issparingly soluble or insoluble and which is in a volume amount of lessthan 10 times (preferably a volume amount of 5 times or less) the resinsolution A (step d), and separating the precipitated resin (step e).

As for the solvent used at the preparation of the resin solution A, asolvent similar to the solvent used for dissolving the monomer at thepolymerization reaction may be used, and the solvent may be the same asor different from the solvent used at the polymerization reaction.

(E) Basic Compound

The resist composition of the present invention preferably contains (E)a basic compound for reducing the change of performance with aging fromexposure to heating.

Preferred examples of the basic compound include compounds having astructure represented by any one of the following formulae (A) to (E):

In formulae (A) and (E), each of R²⁰⁰, R²⁰¹ and R²⁰² which may be thesame or different represents a hydrogen atom, an alkyl group (preferablyhaving a carbon number of 1 to 20), a cycloalkyl group (preferablyhaving a carbon number of 3 to 20) or an aryl group (having a carbonnumber of 6 to 20), and R²⁰¹ and R²⁰² may combine with each other toform a ring.

As for the alkyl group, the alkyl group having a substituent ispreferably an aminoalkyl group having a carbon number of 1 to 20, ahydroxyalkyl group having a carbon number of 1 to 20, or a cyanoalkylgroup having a carbon number of 1 to 20.

Each of R²⁰³, R²⁰⁴, R²⁰⁵ and R²⁰⁶ which may be the same or differentrepresents an alkyl group having a carbon number of 1 to 20.

The alkyl group in these formulae (A) and (E) is more preferablyunsubstituted.

Preferred examples of the compound include guanidine, aminopyrrolidine,pyrazole, pyrazoline, piperazine, aminomorpholine, aminoalkylmorpholineand piperidine. More preferred examples of the compound include acompound having an imidazole structure, a diazabicyclo structure, anonium hydroxide structure, an onium carboxylate structure, atrialkylamine structure, an aniline structure or a pyridine structure;an alkylamine derivative having a hydroxyl group and/or an ether bond;and an aniline derivative having a hydroxyl group and/or an ether bond.

Examples of the compound having an imidazole structure includeimidazole, 2,4,5-triphenylimidazole and benzimidazole. Examples of thecompound having a diazabicyclo structure include1,4-diazabicyclo[2,2,2]octane, 1,5-diazabicyclo[4,3,0]non-5-ene and1,8-diazabicyclo[5,4,0]undec-7-ene. Examples of the compound having anonium hydroxide structure include triarylsulfonium hydroxide,phenacylsulfonium hydroxide and sulfonium hydroxide having a 2-oxoalkylgroup, specifically, triphenylsulfonium hydroxide,tris(tert-butylphenyl)sulfonium hydroxide, bis(tert-butylphenyl)iodoniumhydroxide, phenacylthiophenium hydroxide and 2-oxopropylthiopheniumhydroxide. Examples of the compound having an onium carboxylatestructure include a compound where the anion moiety of the compoundhaving an onium hydroxide structure is converted into a carboxylate,such as acetate, adamantane-1-carboxylate and perfluoroalkylcarboxylate. Examples of the compound having a trialkylamine structureinclude tri(n-butyl)amine and tri(n-octyl)amine. Examples of the anilinecompound include 2,6-diisopropylaniline, N,N-dimethylaniline,N,N-dibutylaniline and N,N-dihexylaniline. Examples of the alkylaminederivative having a hydroxyl group and/or an ether bond includeethanolamine, diethanolamine, triethanolamine andtris(methoxyethoxyethyl)amine. Examples of the aniline derivative havinga hydroxyl group and/or an ether bond includeN,N-bis(hydroxyethyl)aniline.

One of these basic compounds is used alone, or two or more kinds thereofare used in combination.

The amount of the basic compound used is usually from 0.001 to 10 mass%, preferably from 0.01 to 5 mass %, based on the solid content of theresist composition.

The ratio between the acid generator and the basic compound used in thecomposition is preferably acid generator/basic compound (by mol)=from2.5 to 300. That is, the molar ratio is preferably 2.5 or more in viewof sensitivity and resolution and preferably 300 or less from thestandpoint of suppressing the reduction in resolution due to thickeningof the resist pattern with aging after exposure until heat treatment.The acid generator/basic compound (by mol) is more preferably from 5.0to 200, still more preferably from 7.0 to 150.

(F) Surfactant

The resist composition of the present invention preferably furthercontains (F) a surfactant, more preferably any one fluorine-containingand/or silicon-containing surfactant (a fluorine-containing surfactant,a silicon-containing surfactant or a surfactant containing both afluorine atom and a silicon atom) or two or more kinds thereof.

When the resist composition of the present invention contains thesurfactant (F), a resist pattern with good sensitivity, resolution andadherence as well as less development defects can be obtained in usingan exposure light source of 250 nm or less, particularly 220 nm or less.

Examples of the fluorine-containing and/or silicon-containing surfactantinclude surfactants described in JP-A-62-36663, JP-A-61-226746,JP-A-61-226745, JP-A-62-170950, JP-A-63-34540, JP-A-7-230165,JP-A-8-62834, JP-A-9-54432, JP-A-9-5988, JP-A-2002-277862 and U.S. Pat.Nos. 5,405,720, 5,360,692, 5,529,881, 5,296,330, 5,436,098, 5,576,143,5,294,511 and 5,824,451. The following commercially availablesurfactants each may also be used as it is.

Examples of the commercially available surfactant which can be usedinclude a fluorine-containing or silicon-containing surfactant such asEFtop EF301 and EF303 (produced by Shin-Akita Kasei K.K.); Florad FC430,431 and 4430 (produced by Sumitomo 3M Inc.); Megaface F171, F173, F176,F189, F113, F110, F177, F120 and R08 (produced by Dainippon Ink &Chemicals, Inc.); Surflon S-382, SC101, 102, 103, 104, 105 and 106(produced by Asahi Glass Co., Ltd.); Troysol S-366 (produced by TroyChemical); GF-300 and GF-150 (produced by Toagosei Chemical IndustryCo., Ltd.); Surflon S-393 (produced by Seimi Chemical Co., Ltd.); EftopEF121, EF122A, EF122B, RF122C, EF125M, EF135M, EF351, 352, EF801, EF802and EF601 (produced by JEMCO Inc.); PF636, PF656, PF6320 and PF6520(produced by OMNOVA); and FTX-204D, 208G, 218G, 230G, 204D, 208D, 212D,218 and 222D (produced by NEOS Co., Ltd.). In addition, polysiloxanepolymer KP-341 (produced by Shin-Etsu Chemical Co., Ltd.) may also beused as the silicon-containing surfactant.

Other than those known surfactants, a surfactant using a polymer havinga fluoro-aliphatic group derived from a fluoro-aliphatic compound whichis produced by a telomerization process (also called a telomer process)or an oligomerization process (also called an oligomer process), may beused. The fluoro-aliphatic compound can be synthesized by the methoddescribed in JP-A-2002-90991.

The polymer having a fluoro-aliphatic group is preferably a copolymer ofa fluoro-aliphatic group-containing monomer with a (poly(oxyalkylene))acrylate and/or a (poly(oxyalkylene)) methacrylate, and the copolymermay have an irregular distribution or may be a block copolymer. Examplesof the poly(oxyalkylene) group include a poly(oxyethylene) group, apoly(oxypropylene) group and a poly(oxybutylene) group. This group mayalso be a unit having alkylenes differing in the chain length within thesame chain, such as block-linked poly(oxyethylene, oxypropylene andoxyethylene) and block-linked poly(oxyethylene and oxypropylene).Furthermore, the copolymer of a fluoro-aliphatic group-containingmonomer and a (poly(oxyalkylene)) acrylate (or methacrylate) is notlimited only to a binary copolymer but may also be a ternary or greatercopolymer obtained by simultaneously copolymerizing two or moredifferent fluoro-aliphatic group-containing monomers or two or moredifferent (poly(oxyalkylene)) acrylates (or methacrylates).

Examples thereof include, as the commercially available surfactant,Megaface F178, F-470, F-473, F-475, F-476 and F-472 (produced byDainippon Ink & Chemicals, Inc.) and further include a copolymer of aC₆F₁₃ group-containing acrylate (or methacrylate) with a(poly(oxyalkylene)) acrylate (or methacrylate), and a copolymer of aC₃F₇ group-containing acrylate (or methacrylate) with a(poly(oxyethylene)) acrylate (or methacrylate) and a(poly(oxypropylene)) acrylate (or methacrylate).

In the present invention, a surfactant other than thefluorine-containing and/or silicon-containing surfactant may also beused. Specific examples thereof include a nonionic surfactant such aspolyoxyethylene alkyl ethers (e.g., polyoxyethylene lauryl ether,polyoxyethylene stearyl ether, polyoxyethylene cetyl ether,polyoxyethylene oleyl ether), polyoxyethylene alkylaryl ethers (e.g.,polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether),polyoxyethyleneepolyoxypropylene block copolymers, sorbitan fatty acidesters (e.g., sorbitan monolaurate, sorbitan monopalmitate, sorbitanmonostearate, sorbitan monooleate, sorbitan trioleate, sorbitantristearate) and polyoxyethylene sorbitan fatty acid esters (e.g.,polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitanmonopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylenesorbitan trioleate, polyoxyethylene sorbitan tristearate).

One of these surfactants may be used alone, or several surfactants maybe used in combination.

The amount of the surfactant (F) used is preferably from 0.01 to 10 mass%, more preferably from 0.1 to 5 mass %, based on the entire amount ofthe resist composition (excluding the solvent).

(G) Onium Carboxylate

The resist composition of the present invention may contain (G) an oniumcarboxylate. Examples of the onium carboxylate include sulfoniumcarboxylate, iodonium carboxylate and ammonium carboxylate. Inparticular, the onium carboxylate (G) is preferably an iodonium salt ora sulfonium salt. Furthermore, the carboxylate residue of the oniumcarboxylate (G) for use in the present invention preferably contains noaromatic group and no carbon-carbon double bond. The anion moiety ispreferably a linear, branched, monocyclic or polycyclic alkylcarboxylateanion having a carbon number of 1 to 30, more preferably an anion of thecarboxylic acid with the alkyl group being partially or entirelyfluorine-substituted. The alkyl chain may contain an oxygen atom. Thanksto such a construction, the transparency to light of 220 nm or less isensured, the sensitivity and resolution are enhanced, and the iso/densebias and exposure margin are improved.

Examples of the anion of the fluorine-substituted carboxylic acidinclude anions of fluoroacetic acid, difluoroacetic acid,trifluoroacetic acid, pentafluoropropionic acid, heptafluorobutyricacid, nonafluoropentanoic acid, perfluorododecanoic acid,perfluorotridecanoic acid, perfluorocyclohexanecarboxylic acid and2,2-bistrifluoromethylpropionic acid.

These onium carboxylates (G) can be synthesized by reacting a sulfonium,iodonium or ammonium hydroxide and a carboxylic acid with silver oxidein an appropriate solvent.

The content of the onium carboxylate (G) in the composition is generallyfrom 0.1 to 20 mass %, preferably from 0.5 to 10 mass %, more preferablyfrom 1 to 7 mass %, based on the entire solid content of thecomposition.

(H) Other Additives

The resist composition of the present invention may further contain, forexample, a dye, a plasticizer, a photosensitizer, a light absorber, analkali-soluble resin, a dissolution inhibitor and a compound foraccelerating dissolution in a developer (for example, a phenol compoundhaving a molecular weight of 1,000 or less, or a carboxylgroup-containing alicyclic or aliphatic compound), if desired.

The phenol compound having a molecular weight of 1,000 or less can beeasily synthesized by one skilled in the art with reference to themethods described, for example, in JP-A-4-122938, JP-A-2-28531, U.S.Pat. No. 4,916,210 and European Patent 219294.

Specific examples of the carboxyl group-containing alicyclic oraliphatic compound include, but are not limited to, a carboxylic acidderivative having a steroid structure, such as cholic acid, deoxycholicacid and lithocholic acid, an adamantanecarboxylic acid derivative, anadamantanedicarboxylic acid, a cyclohexanecarboxylic acid and acyclohexanedicarboxylic acid.

EXAMPLES

The present invention is described below by referring to Examples, butthe present invention should not be construed as being limited thereto.

Synthesis Example 1 Synthesis of Resin (A1)

Under a nitrogen stream, 8.4 g of methyl isobutyl ketone was chargedinto a three-neck flask and heated at 80° C. Thereto, a solutionobtained by dissolving 9.4 g of 2-(1-adamantyl)propan-2-yl methacrylate,4.5 g of 3,5-dihydroxy-1-adamantyl methacrylate, 6.1 g ofβ-methacryloyloxy-γ-butyrolactone and azobisisobutyronitrilecorresponding to 6 mol % based on the entire monomer amount, in 75.3 gof methyl isobutyl ketone was added dropwise over 6 hours. After thecompletion of dropwise addition, the reaction was further allowed toproceed at 80° C. for 2 hours. The resulting reaction solution wasallowed to cool and then poured in 720 ml of heptane/80 ml of ethylacetate, and the powder precipitated was collected by filtration anddried, as a result, 18.3 g of Resin (A1) was obtained. The weightaverage molecular weight of the obtained resin was 7,000 and thedispersity (Mw/Mn) was 1.80.

Synthesis Example 2 Synthesis of Resin (A2)

Under a nitrogen stream, 8.4 g of methyl isobutyl ketone was chargedinto a three-neck flask and heated at 80° C. Thereto, a solutionobtained by dissolving 9.4 g of 2-(1-adamantyl)propan-2-yl methacrylate,4.5 g of 3,5-dihydroxy-1-adamantyl methacrylate, 6.1 g ofβ-methacryloyloxy-γ-butyrolactone and azobisisobutyronitrilecorresponding to 7 mol % based on the entire monomer amount, in 75.3 gof methyl isobutyl ketone was added dropwise over 6 hours. After thecompletion of dropwise addition, the reaction was further allowed toproceed at 80° C. for 2 hours. The resulting reaction solution wasallowed to cool and then poured in 680 ml of heptane/120 ml of ethylacetate, and the powder precipitated was collected by filtration anddried, as a result, 17.5 g of Resin (A2) was obtained. The weightaverage molecular weight of the obtained resin was 5,800 and thedispersity (Mw/Mn) was 1.53.

Synthesis Example 3 Synthesis of Resin (A3)

Under a nitrogen stream, 19.4 g of methyl isobutyl ketone was chargedinto a three-neck flask and heated at 80° C. Thereto, a solutionobtained by dissolving 9.4 g of 2-(1-adamantyl)propan-2-yl methacrylate,4.5 g of 3,5-dihydroxy-1-adamantyl methacrylate, 6.1 g ofβ-methacryloyloxy-γ-butyrolactone and azobisisobutyronitrilecorresponding to 12 mol % based on the entire monomer amount, in 65.3 gof methyl isobutyl ketone was added dropwise over 8 hours. After thecompletion of dropwise addition, the reaction was further allowed toproceed at 80° C. for 2 hours. The resulting reaction solution wasallowed to cool and then poured in 720 ml of heptane/80 ml of ethylacetate, and the powder precipitated was collected by filtration anddried, as a result, 15.5 g of Resin (A3) was obtained. The weightaverage molecular weight of the obtained resin was 2,800 and thedispersity (Mw/Mn) was 1.26.

Synthesis Example 4 Synthesis of Resin (A4)

Under a nitrogen stream, 8.4 g of methyl isobutyl ketone was chargedinto a three-neck flask and heated at 80° C. Thereto, a solutionobtained by dissolving 9.4 g of 2-(1-adamantyl)propan-2-yl methacrylate,4.5 g of 3,5-dihydroxy-1-adamantyl methacrylate, 6.1 g ofβ-methacryloyloxy-γ-butyrolactone and azobisisobutyronitrilecorresponding to 6 mol % based on the entire monomer amount, in 75.3 gof methyl isobutyl ketone was added dropwise over 6 hours. After thecompletion of dropwise addition, the reaction was further allowed toproceed at 80° C. for 2 hours. The resulting reaction solution wasallowed to cool and then poured in 680 ml of heptane/120 ml of ethylacetate, and the powder precipitated was collected by filtration anddried, as a result, 17.6 g of Resin (A4) was obtained. The weightaverage molecular weight of the obtained resin was 7,000 and thedispersity (Mw/Mn) was 1.55.

Synthesis Example 5 Synthesis of Resin (A5)

Under a nitrogen stream, 8.4 g of methyl isobutyl ketone was chargedinto a three-neck flask and heated at 80° C. Thereto, a solutionobtained by dissolving 9.4 g of 2-(1-adamantyl)propan-2-yl methacrylate,4.5 g of 3,5-dihydroxy-1-adamantyl methacrylate, 6.1 g ofβ-methacryloyloxy-γ-butyrolactone and azobisisobutyronitrilecorresponding to 7 mol % based on the entire monomer amount, in 75.3 gof methyl isobutyl ketone was added dropwise over 6 hours. After thecompletion of dropwise addition, the reaction was further allowed toproceed at 80° C. for 2 hours. The resulting reaction solution wasallowed to cool and then poured in 720 ml of heptane/80 ml of ethylacetate, and the powder precipitated was collected by filtration anddried, as a result, 18.5 g of Resin (A5) was obtained. The weightaverage molecular weight of the obtained resin was 6,000 and thedispersity (Mw/Mn) was 1.75.

Resist Composition (A1):

A solution having a solid content concentration of 5.8 mass % obtainedby dissolving the components shown below in a mixed solvent of propyleneglycol monomethyl ether acetate/propylene glycol monomethyl ether(60:40) was filtered through a polyethylene filter having a pore size of0.1 μm to prepare Resist Composition (A1).

Resin (A1): 1.83 g, triphenylsulfonium nonaflate: 69.6 mg,diphenylaniline: 8.7 mg, and PF6320 (fluorine-containing surfactantproduced by OMNOVA): 1.7 mg.

Resist Compositions (A2) to (A5):

Resist Compositions (A2) to (A5) were prepared in the same manner exceptfor using Resins (A2) to (A5) in place of Resin (A1).

Comparative Example 1

An organic antireflection film, ARC29A (produced by Nissan ChemicalIndustries, Ltd.), was coated on a 8-inch silicon wafer and baked at205° C. for 60 seconds to form an antireflection film having a thicknessof 78 nm, and Resist Composition (A1) prepared above was coated thereonand baked at 120° C. for 60 seconds to form a resist film having athickness of 150 nm. The obtained wafer was subjected to patternexposure using an ArF excimer laser scanner (NA: 0.75). Thereafter, theresist film was heated at 120° C. for 60 seconds, developed with anaqueous tetramethylammonium hydroxide solution (2.38 mass %) (positivetone developer) for 30 seconds (positive tone development), and rinsedwith pure water to obtain a pattern having a pitch of 600 nm and a linewidth of 450 nm. Furthermore, the resist film was developed with butylacetate (negative tone developer) for 30 seconds (negative tonedevelopment) and rinsed with 1-hexanol (rinsing solution for negativetone development) for 30 seconds, and thereafter, the wafer was rotatedat a rotation number of 3,000 rpm for 30 seconds to obtain a 150-nm(1:1) line-and-space resist pattern.

Examples 1 to 4

In the same manner as in Comparative Example 1, 150-nm (1:1) resistpatterns were obtained using Resist Compositions (A2) to (A5),respectively.

Evaluation of Line Edge Roughness (LER):

The 150-nm (1:1) line-and-space resist patterns obtained in ComparativeExample 1 and Examples 1 to 4 were observed by a scanning microscope(S9260, manufactured by Hitachi Ltd.). With respect to the range of 2 μmedge in the longitudinal direction of the 150-nm line pattern, thedistance from the reference line where the edge should be present wasmeasured at 50 points and after determining the standard deviation, 3σ(unit: nm) was calculated. A smaller value indicates better performance.

The results are shown in Table 1.

TABLE 1 Resist Molecular LER Composition Resin Weight Dispersity (nm)Comparative A1 A1 7000 1.80 9.5 Example 1 Example 1 A2 A2 5800 1.53 6.8Example 2 A3 A3 2800 1.26 5.2 Example 3 A4 A4 7000 1.55 7.0 Example 4 A5A5 6000 1.75 7.1

Example 5

An organic antireflection film, ARC29A (produced by Nissan ChemicalIndustries, Ltd.), was coated on a 8-inch silicon wafer and baked at205° C. for 60 seconds to form an antireflection film having a thicknessof 78 nm, and Resist Composition (A2) prepared above was coated thereonand baked at 120° C. for 60 seconds to form a resist film having athickness of 150 nm. The obtained wafer was subjected to patternexposure using an ArF excimer laser scanner (NA: 0.75). Thereafter, theresist film was heated at 120° C. for 60 seconds, developed with anaqueous tetramethylammonium hydroxide solution (2.38 mass %) (positivetone developer) for 30 seconds (positive tone development), and rinsedwith pure water to obtain a pattern having a pitch of 600 nm and a linewidth of 450 nm. Furthermore, the resist film was developed with ethylacetate (negative tone developer) for 30 seconds (negative tonedevelopment) and rinsed with 1-hexanol (rinsing solution for negativetone development) for 30 seconds, and thereafter, the wafer was rotatedat a rotation number of 3,000 rpm for 30 seconds to obtain a 150-nm(1:1) line-and-space resist pattern.

Examples 6 to 18

In the same manner as in Example 5, 150-nm (1:1) resist patterns wereobtained by using Resist Composition (A2) and combining the negativetone developer and the rinsing solution for negative tone development asshown in Table 2.

Evaluation of Dimensional Uniformity:

The 150-nm (1:1) line-and-space resist patterns obtained in Examples 1and 5 to 18 each was measured for the dimension at 50 portions atintervals of 2 nm by using a scanning microscope (S9260, manufactured byHitachi Ltd.). The standard deviation of 50 portions was determined, and3σ (unit: nm) was calculated. A smaller value indicates betterperformance. The results are shown in Table 2.

TABLE 2 Rinsing Solution Dimensional Negative Tone for NegativeUniformity Developer Tone Development (nm) Example 1 butyl acetate1-hexanol 3.1 Example 5 ethyl acetate 1-hexanol 8.4 Example 6 isoamylacetate 1-hexanol 3.1 Example 7 methyl isobutyl ketone 1-hexanol 3.5Example 8 2-hexanone 1-hexanol 2.7 Example 9 methyl ethyl ketone1-hexanol 9.6 Example 10 dipropyl ether 1-hexanol 11.6 Example 11dibutyl ether 1-hexanol 4.2 Example 12 butyl acetate/2- 1-hexanol 3.5hexanone (80/20) Example 13 isoamyl acetate/ 1-hexanol 3.8 dibutyl ether(70/30) Example 14 isoamyl acetate 1-heptanol 8.8 Example 15 isoamylacetate 2-heptanol 3.3 Example 16 isoamyl acetate decane 4.3 Example 17isoamyl acetate dodecane 9.2 Example 18 isoamyl acetate 1-heptanol/ 3.7decane (50/50)

The vapor pressure and boiling point of each of the solvent for negativetone developer and the solvent for rinsing solution for negative tonedevelopment used in Examples 1 and 5 to 18 are shown in Table 3.

TABLE 3 Solvent Name Vapor Pressure (20° C.) Boiling Point butyl acetate1.2 kPa 126° C. ethyl acetate 10 kPa 77° C. isoamyl acetate 0.53 kPa142° C. methyl isobutyl ketone 2.1 kPa 117-118° C. 2-hexanone 0.36 kPa126-128° C. methyl ethyl ketone 10.5 kPa 80° C. dipropyl ether 8.3 kPa88-90° C. dibutyl ether 0.64 kPa 142° C. 1-hexanol 0.13 kPa 157° C.1-heptanol 0.015 kPa 175° C. 2-heptanol 0.13 kPa 150-160° C. decane 0.17kPa 174.2° C. dodecane 0.040 kPa 216.2° C.

Comparative Example 2

An organic antireflection film, ARC29A (produced by Nissan ChemicalIndustries, Ltd.), was coated on a 8-inch silicon wafer and baked at205° C. for 60 seconds to form an antireflection film having a thicknessof 78 nm, and Resist Composition (A1) prepared above was coated thereonand baked at 120° C. for 60 seconds to form a resist film having athickness of 150 nm. The obtained wafer was subjected to patternexposure using an ArF excimer laser scanner (NA: 0.75). Subsequently,the resist film was developed with butyl acetate (negative tonedeveloper) for 30 seconds (negative tone development) and rinsed with1-hexanol (rinsing solution for negative tone development) for 30seconds, and thereafter, the wafer was rotated at a rotation number of3,000 rpm for 30 seconds to obtain a pattern having a pitch of 400 nmand a line width of 200 nm.

Examples 20 to 29

In the same manner as in Comparative Example 2, patterns having a pitch400 nm and a line width of 200 nm were obtained using ResistCompositions (A2) to (A5) and (B1) to (B6), respectively. Theformulations of Resist Compositions (A2) to (A5) are as described above,and the formulations of Resist Compositions (B1) to (B6) were preparedin the same manner as Resist Composition (A1) except for changing theformulation to the formulations shown in Table 5 below.

Evaluation of Line Edge Roughness (LER):

The patterns having a pitch of 400 nm and a line width of 200 nmobtained in Comparative Example 2 and Examples 20 to 29 were observed bya scanning microscope (S9260, manufactured by Hitachi Ltd.). Withrespect to the range of 2 μm edge in the longitudinal direction of the200-nm line pattern, the distance from the reference line where the edgeshould be present was measured at 50 points and after determining thestandard deviation, 3σ (unit: nm) was calculated. A smaller valueindicates better performance. The results are shown in Tables 4 and 5.

TABLE 4 Resist Molecular LER Composition Resin Weight Dispersity (nm)Comparative A1 A1 7000 1.80 8.9 Example 2 Example 20 A2 A2 5800 1.53 6.3Example 21 A3 A3 2800 1.26 5.3 Example 22 A4 A4 7000 1.55 7.2 Example 23A5 A5 6000 1.75 7.4

TABLE 5 Acid Basic Solvent Resist Resin Generator Compound Surfactant(mass LER Example Composition (10 g) (g) (g) (0.02 g) ratio) (nm) 24 B1A6 PAG-A PEA (0.05) W-5 A1/B1 6.0 (0.50) (60/40) 25 B2 A7 PAG-E DIA(0.05) W-2 A1/B2 5.8 (0.40) (40/60) 26 B3 A8 PAG-B TPA (0.06) W-6 A2/B36.3 (0.80) (95/5) 27 B4 A9 PAG-C PBI (0.07) W-1 A2/B1 6.1 (0.60) (50/50)28 B5 A7 PAG-F DIA (0.10) W-4 A2/B2 6.5 (0.20) (40/60) 29 B6 A9 PAG-DTOA W-3 A1/B3 6.2 (0.90) (0.08) (90/10)

The abbreviations used in Examples indicate those set forth as specificexamples above or the followings.

TABLE 6 Compositional No. Monomer (1) Monomer (2) Monomer (3) Ratio (bymol) Mw Mw/Mn A6

30/30/40 5000 1.4 A7

50/20/30 5500 1.5 A8

50/10/40 4800 1.5 A9

40/20/40 5300 1.6

DIA: 2,6-diisopropylanilineTPA: tripentylamine

PEA: N-phenyldiethanolamine

TOA: trioctylaminePBI: 2-phenylbenzimidazoleW-1: Megaface F176 (produced by Dainippon Ink & Chemicals, Inc.)(fluorine-containing)W-2: Megaface R08 (produced by Dainippon Ink & Chemicals, Inc.)(fluorine and silicon-containing)W-3: Polysiloxane Polymer KP-341 (produced by Shin-Etsu Chemical Co.,Ltd.) (silicon-containing)W-4: Troysol S-366 (produced by Troy Chemical)W-5: PF656 (produced by OMNOVA, fluorine-containing)W-6: PF6320 (produced by OMNOVA, fluorine-containing)A1: propylene glycol monomethyl ether acetateA2: cyclohexanoneB1: propylene glycol monomethyl etherB2: ethyl lactateB3: γ-butyrolactone

As apparent from these Examples, thanks to the combination of resistcomposition, negative tone developer and rinsing solution for negativetone development of the present invention, the line edge roughness isreduced and furthermore, the dimensional uniformity is high.

INDUSTRIAL APPLICABILITY

By the pattern forming method and the resist composition of the presentinvention, a pattern with reduced line edge roughness and highdimensional uniformity is obtained. In particular, a highly practicalnegative tone development technique and a double development techniqueusing the same are provided. These techniques enables finer patterningunder the same light source as that in conventional technology. Thepattern forming method of the present invention is suitably used in theprocess of producing a semiconductor such as IC, in the production of acircuit board for liquid crystal, thermal head and the like, and in thelithography process of other photofabrications.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

1. A pattern forming method, comprising: (i) a step of applying a resistcomposition whose solubility in a negative tone developer decreases uponirradiation with an actinic ray or radiation and which contains a resinhaving an alicyclic hydrocarbon structure and a dispersity of 1.7 orless and being capable of increasing a polarity of the resin by anaction of an acid; (ii) an exposure step; and (iv) a development stepusing a negative tone developer.
 2. A pattern forming method,comprising: (i) a step of applying a resist composition whose solubilityin a negative tone developer decreases upon irradiation with an actinicray or radiation and which contains a resin having an alicyclichydrocarbon structure and a weight average molecular weight of 6,000 orless and being capable of increasing a polarity of the resin by anaction of an acid; (ii) an exposure step; and (iv) a development stepusing a negative tone developer.
 3. A pattern forming method,comprising: (i) a step of applying a resist composition whose solubilityin a negative tone developer decreases upon irradiation with an actinicray or radiation and which contains a resin having an alicyclichydrocarbon structure, a dispersity of 1.7 or less and a weight averagemolecular weight of 6,000 or less and being capable of increasing apolarity of the resin by an action of an acid; (ii) an exposure step;and (iv) a development step using a negative tone developer.
 4. Thepattern forming method according to any one of claims 1 to 3, wherein(iv) the development step using a negative tone developer is a stepperformed using a developer containing at least one kind of a solventselected from organic solvents and having a vapor pressure of 5.0 kPa orless at 20° C.
 5. The pattern forming method according to any one ofclaims 1 to 3, which further comprises: (vi) a washing step using arinsing solution containing an organic solvent.
 6. The pattern formingmethod according to claim 5, wherein the rinsing solution containing anorganic solvent is a rinsing solution having a vapor pressure of 0.1 kPaor more at 20° C.
 7. The pattern forming method according to any one ofclaims 1 to 3, which further comprises: (iii) a development step using apositive tone developer.
 8. A resist composition for negative tonedevelopment, comprising: (a1) a resin having an alicyclic hydrocarbonstructure and a dispersity of 1.7 or less and being capable ofincreasing a polarity of the resin by an action of an acid; (B) aphoto-acid generator; and (C) a solvent.
 9. A resist composition fornegative tone development, comprising: (a2) a resin having an alicyclichydrocarbon structure and a weight average molecular weight of 6,000 orless and being capable of increasing a polarity of the resin by anaction of an acid; (B) a photo-acid generator; and (C) a solvent.
 10. Aresist composition for negative tone development, comprising: (a3) aresin having an alicyclic hydrocarbon structure, a dispersity of 1.7 orless and a weight average molecular weight of 6,000 or less and beingcapable of increasing a polarity of the resin by an action of an acid;(B) a photo-acid generator; and (C) a solvent.
 11. A resist compositionfor multiple development, comprising: (a1) a resin having an alicyclichydrocarbon structure and a dispersity of 1.7 or less and being capableof increasing a polarity of the resin by an action of an acid; (B) aphoto-acid generator; and (C) a solvent.
 12. A resist composition formultiple development, comprising: (a2) a resin having an alicyclichydrocarbon structure and a weight average molecular weight of 6,000 orless and being capable of increasing a polarity of the resin by anaction of an acid; (B) a photo-acid generator; and (C) a solvent.
 13. Aresist composition for multiple development, comprising: (a3) a resinhaving an alicyclic hydrocarbon structure, a dispersity of 1.7 or lessand a weight average molecular weight of 6,000 or less and being capableof increasing a polarity of the resin by an action of an acid; (B) aphoto-acid generator; and (C) a solvent.
 14. A developer for negativetone development, which is used in the pattern forming method claimed inany one of claims 1 to 3, the developer comprising an organic solventand having a vapor pressure of 5 kPa or less at 20° C.
 15. A rinsingsolution for negative tone development, which is used in the patternforming method claimed in any one of claims 1 to 3, the rinsing solutioncomprising an organic solvent and having a vapor pressure of 0.1 kPa ormore at 20° C.
 16. The pattern forming method according to any one ofclaims 1 to 3, wherein (ii) the exposure step is performed by using anArF excimer laser.
 17. The pattern forming method according to any oneof claims 1 to 3, wherein the negative tone developer is at least oneselected from the group consisting of ketone-based solvent, ester-basedsolvent, alcohol-based solvent, amide-based solvent, ether-based solventand hydrocarbon-based solvent.